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	$189.76	3.322%	$196.0638	$196.06	$196.05	$196.10
Purchase #2	$60.57	11.406%	$67.4786	$67.48	$67.50	$67.50
Purchase #3	$182.63	8.143%	$197.5016	$197.50	$197.50	$197.50
Purchase #4	$231.54	7.802%	$249.6048	$249.60	$249.60	$249.60
Purchase #5	$179.38	10.170%	$197.6229	$197.62	$197.60	$197.60
Purchase #6	$12.95	13.728%	$14.7278	$14.73	$14.75	$14.70
Purchase #7	$53.89	6.409%	$57.3438	$57.34	$57.35	$57.30
7 purchase totals =	$910.72		$980.3433	$980.33	$980.35	$980.30