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	$103.78	11.512%	$115.7272	$115.73	$115.75	$115.70
Purchase #2	$153.46	13.299%	$173.8686	$173.87	$173.85	$173.90
Purchase #3	$41.96	3.603%	$43.4718	$43.47	$43.45	$43.50
Purchase #4	$127.43	13.290%	$144.3654	$144.37	$144.35	$144.40
Purchase #5	$82.26	11.344%	$91.5916	$91.59	$91.60	$91.60
Purchase #6	$134.70	6.450%	$143.3882	$143.39	$143.40	$143.40
Purchase #7	$142.99	11.831%	$159.9071	$159.91	$159.90	$159.90
7 purchase totals =	$786.58		$872.3199	$872.33	$872.30	$872.40