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	$87.55	11.178%	$97.3363	$97.34	$97.35	$97.30
Purchase #2	$40.90	12.678%	$46.0853	$46.09	$46.10	$46.10
Purchase #3	$94.56	6.530%	$100.7348	$100.73	$100.75	$100.70
Purchase #4	$154.48	8.360%	$167.3945	$167.39	$167.40	$167.40
Purchase #5	$130.29	10.367%	$143.7972	$143.80	$143.80	$143.80
Purchase #6	$216.62	9.592%	$237.3982	$237.40	$237.40	$237.40
Purchase #7	$238.65	12.516%	$268.5194	$268.52	$268.50	$268.50
7 purchase totals =	$963.05		$1,061.2657	$1,061.27	$1,061.30	$1,061.20