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	$48.64	7.697%	$52.3838	$52.38	$52.40	$52.40
Purchase #2	$151.57	13.157%	$171.5121	$171.51	$171.50	$171.50
Purchase #3	$160.49	12.480%	$180.5192	$180.52	$180.50	$180.50
Purchase #4	$62.38	7.345%	$66.9618	$66.96	$66.95	$67.00
Purchase #5	$219.41	6.281%	$233.1911	$233.19	$233.20	$233.20
Purchase #6	$237.54	5.568%	$250.7662	$250.77	$250.75	$250.80
Purchase #7	$73.66	4.171%	$76.7324	$76.73	$76.75	$76.70
7 purchase totals =	$953.69		$1,032.0666	$1,032.06	$1,032.05	$1,032.10