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	$209.61	9.317%	$229.1394	$229.14	$229.15	$229.10
Purchase #2	$97.90	8.398%	$106.1216	$106.12	$106.10	$106.10
Purchase #3	$201.46	4.460%	$210.4451	$210.45	$210.45	$210.40
Purchase #4	$47.59	5.751%	$50.3269	$50.33	$50.35	$50.30
Purchase #5	$101.96	3.405%	$105.4317	$105.43	$105.45	$105.40
Purchase #6	$19.81	6.674%	$21.1321	$21.13	$21.15	$21.10
Purchase #7	$247.32	4.523%	$258.5063	$258.51	$258.50	$258.50
7 purchase totals =	$925.65		$981.1031	$981.11	$981.15	$980.90