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	$73.95	10.296%	$81.5639	$81.56	$81.55	$81.60
Purchase #2	$35.49	8.355%	$38.4552	$38.46	$38.45	$38.50
Purchase #3	$246.35	3.694%	$255.4502	$255.45	$255.45	$255.50
Purchase #4	$38.27	10.653%	$42.3469	$42.35	$42.35	$42.30
Purchase #5	$152.26	11.360%	$169.5567	$169.56	$169.55	$169.60
Purchase #6	$226.63	6.138%	$240.5405	$240.54	$240.55	$240.50
Purchase #7	$210.85	4.207%	$219.7205	$219.72	$219.70	$219.70
7 purchase totals =	$983.80		$1,047.6339	$1,047.64	$1,047.60	$1,047.70