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	$133.93	11.446%	$149.2596	$149.26	$149.25	$149.30
Purchase #2	$29.45	3.413%	$30.4551	$30.46	$30.45	$30.50
Purchase #3	$221.65	3.730%	$229.9175	$229.92	$229.90	$229.90
Purchase #4	$6.28	4.179%	$6.5424	$6.54	$6.55	$6.50
Purchase #5	$46.79	6.192%	$49.6872	$49.69	$49.70	$49.70
Purchase #6	$88.79	11.667%	$99.1491	$99.15	$99.15	$99.10
Purchase #7	$189.89	3.487%	$196.5115	$196.51	$196.50	$196.50
7 purchase totals =	$716.78		$761.5224	$761.53	$761.50	$761.50