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	$151.39	10.581%	$167.4086	$167.41	$167.40	$167.40
Purchase #2	$222.64	8.644%	$241.885	$241.89	$241.90	$241.90
Purchase #3	$144.82	4.478%	$151.305	$151.31	$151.30	$151.30
Purchase #4	$170.94	10.363%	$188.6545	$188.65	$188.65	$188.70
Purchase #5	$50.76	11.598%	$56.6471	$56.65	$56.65	$56.60
Purchase #6	$92.71	12.589%	$104.3813	$104.38	$104.40	$104.40
Purchase #7	$47.51	7.544%	$51.0942	$51.09	$51.10	$51.10
7 purchase totals =	$880.77		$961.3757	$961.38	$961.40	$961.40