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	$189.92	3.467%	$196.5045	$196.50	$196.50	$196.50
Purchase #2	$34.85	8.256%	$37.7272	$37.73	$37.75	$37.70
Purchase #3	$190.76	9.541%	$208.9604	$208.96	$208.95	$209.00
Purchase #4	$101.33	4.721%	$106.1138	$106.11	$106.10	$106.10
Purchase #5	$6.82	4.279%	$7.1118	$7.11	$7.10	$7.10
Purchase #6	$199.44	5.133%	$209.6773	$209.68	$209.70	$209.70
Purchase #7	$162.69	8.490%	$176.5024	$176.50	$176.50	$176.50
7 purchase totals =	$885.81		$942.5974	$942.59	$942.60	$942.60