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	$145.94	4.539%	$152.5642	$152.56	$152.55	$152.60
Purchase #2	$61.90	3.687%	$64.1823	$64.18	$64.20	$64.20
Purchase #3	$201.77	10.758%	$223.4764	$223.48	$223.50	$223.50
Purchase #4	$68.64	13.271%	$77.7492	$77.75	$77.75	$77.70
Purchase #5	$59.54	13.522%	$67.591	$67.59	$67.60	$67.60
Purchase #6	$189.89	3.339%	$196.2304	$196.23	$196.25	$196.20
Purchase #7	$27.68	11.108%	$30.7547	$30.75	$30.75	$30.80
7 purchase totals =	$755.36		$812.5482	$812.54	$812.60	$812.60