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	$113.85	12.826%	$128.4524	$128.45	$128.45	$128.50
Purchase #2	$88.66	7.300%	$95.1322	$95.13	$95.15	$95.10
Purchase #3	$186.43	4.431%	$194.6907	$194.69	$194.70	$194.70
Purchase #4	$115.89	13.481%	$131.5131	$131.51	$131.50	$131.50
Purchase #5	$103.84	8.129%	$112.2812	$112.28	$112.30	$112.30
Purchase #6	$143.68	5.633%	$151.7735	$151.77	$151.75	$151.80
Purchase #7	$173.35	13.575%	$196.8823	$196.88	$196.90	$196.90
7 purchase totals =	$925.70		$1,010.7254	$1,010.71	$1,010.75	$1,010.80