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	$149.63	7.363%	$160.6473	$160.65	$160.65	$160.60
Purchase #2	$250.69	11.243%	$278.8751	$278.88	$278.90	$278.90
Purchase #3	$130.71	13.468%	$148.314	$148.31	$148.30	$148.30
Purchase #4	$118.64	3.551%	$122.8529	$122.85	$122.85	$122.90
Purchase #5	$38.72	5.703%	$40.9282	$40.93	$40.95	$40.90
Purchase #6	$40.77	6.483%	$43.4131	$43.41	$43.40	$43.40
Purchase #7	$193.82	13.821%	$220.6079	$220.61	$220.60	$220.60
7 purchase totals =	$922.98		$1,015.6385	$1,015.64	$1,015.65	$1,015.60