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	$190.48	4.635%	$199.3087	$199.31	$199.30	$199.30
Purchase #2	$43.67	7.849%	$47.0977	$47.10	$47.10	$47.10
Purchase #3	$88.81	4.449%	$92.7612	$92.76	$92.75	$92.80
Purchase #4	$127.74	12.354%	$143.521	$143.52	$143.50	$143.50
Purchase #5	$205.31	10.538%	$226.9456	$226.95	$226.95	$226.90
Purchase #6	$50.98	9.470%	$55.8078	$55.81	$55.80	$55.80
Purchase #7	$233.57	9.306%	$255.306	$255.31	$255.30	$255.30
7 purchase totals =	$940.56		$1,020.7480	$1,020.76	$1,020.70	$1,020.70