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	$171.32	10.533%	$189.3651	$189.37	$189.35	$189.40
Purchase #2	$144.36	4.787%	$151.2705	$151.27	$151.25	$151.30
Purchase #3	$153.30	10.519%	$169.4256	$169.43	$169.45	$169.40
Purchase #4	$76.69	11.677%	$85.6451	$85.65	$85.65	$85.60
Purchase #5	$168.48	4.283%	$175.696	$175.70	$175.70	$175.70
Purchase #6	$82.27	7.658%	$88.5702	$88.57	$88.55	$88.60
Purchase #7	$141.32	4.653%	$147.8956	$147.90	$147.90	$147.90
7 purchase totals =	$937.74		$1,007.8681	$1,007.89	$1,007.85	$1,007.90