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	$175.37	12.148%	$196.6739	$196.67	$196.65	$196.70
Purchase #2	$134.82	8.644%	$146.4738	$146.47	$146.45	$146.50
Purchase #3	$91.89	12.760%	$103.6152	$103.62	$103.60	$103.60
Purchase #4	$23.49	7.615%	$25.2788	$25.28	$25.30	$25.30
Purchase #5	$14.96	3.597%	$15.4981	$15.50	$15.50	$15.50
Purchase #6	$198.83	6.693%	$212.1377	$212.14	$212.15	$212.10
Purchase #7	$25.26	12.671%	$28.4607	$28.46	$28.45	$28.50
7 purchase totals =	$664.62		$728.1382	$728.14	$728.10	$728.20