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	$131.43	7.577%	$141.3885	$141.39	$141.40	$141.40
Purchase #2	$149.82	4.213%	$156.1319	$156.13	$156.15	$156.10
Purchase #3	$64.48	11.490%	$71.8888	$71.89	$71.90	$71.90
Purchase #4	$48.66	6.126%	$51.6409	$51.64	$51.65	$51.60
Purchase #5	$209.69	8.272%	$227.0356	$227.04	$227.05	$227.00
Purchase #6	$199.76	11.766%	$223.2638	$223.26	$223.25	$223.30
Purchase #7	$62.26	7.625%	$67.0073	$67.01	$67.00	$67.00
7 purchase totals =	$866.10		$938.3568	$938.36	$938.40	$938.30