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	$211.86	3.180%	$218.5971	$218.60	$218.60	$218.60
Purchase #2	$90.51	5.765%	$95.7279	$95.73	$95.75	$95.70
Purchase #3	$20.77	3.400%	$21.4762	$21.48	$21.50	$21.50
Purchase #4	$165.74	4.845%	$173.7701	$173.77	$173.75	$173.80
Purchase #5	$203.52	5.649%	$215.0168	$215.02	$215.00	$215.00
Purchase #6	$96.75	4.329%	$100.9383	$100.94	$100.95	$100.90
Purchase #7	$172.54	3.628%	$178.7998	$178.80	$178.80	$178.80
7 purchase totals =	$961.69		$1,004.3262	$1,004.34	$1,004.35	$1,004.30