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	$181.84	8.311%	$196.9527	$196.95	$196.95	$197.00
Purchase #2	$127.78	11.690%	$142.7175	$142.72	$142.70	$142.70
Purchase #3	$168.89	5.460%	$178.1114	$178.11	$178.10	$178.10
Purchase #4	$84.88	4.317%	$88.5443	$88.54	$88.55	$88.50
Purchase #5	$244.50	10.350%	$269.8058	$269.81	$269.80	$269.80
Purchase #6	$211.88	7.294%	$227.3345	$227.33	$227.35	$227.30
Purchase #7	$65.26	12.596%	$73.4801	$73.48	$73.50	$73.50
7 purchase totals =	$1,085.03		$1,176.9463	$1,176.94	$1,176.95	$1,176.90