Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$183.90	3.721%	$190.7429	$190.74	$190.75	$190.70
Purchase #2	$222.81	3.164%	$229.8597	$229.86	$229.85	$229.90
Purchase #3	$180.77	11.118%	$200.868	$200.87	$200.85	$200.90
Purchase #4	$196.90	11.873%	$220.2779	$220.28	$220.30	$220.30
Purchase #5	$211.54	3.805%	$219.5891	$219.59	$219.60	$219.60
Purchase #6	$185.55	12.758%	$209.2225	$209.22	$209.20	$209.20
Purchase #7	$152.98	10.751%	$169.4269	$169.43	$169.45	$169.40
7 purchase totals =	$1,334.45		$1,439.9870	$1,439.99	$1,440.00	$1,440.00