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	$198.36	13.510%	$225.1584	$225.16	$225.15	$225.20
Purchase #2	$186.26	5.469%	$196.4466	$196.45	$196.45	$196.40
Purchase #3	$64.53	4.123%	$67.1906	$67.19	$67.20	$67.20
Purchase #4	$117.46	8.360%	$127.2797	$127.28	$127.30	$127.30
Purchase #5	$193.41	7.207%	$207.3491	$207.35	$207.35	$207.30
Purchase #6	$131.77	7.433%	$141.5645	$141.56	$141.55	$141.60
Purchase #7	$222.86	3.575%	$230.8272	$230.83	$230.85	$230.80
7 purchase totals =	$1,114.65		$1,195.8161	$1,195.82	$1,195.85	$1,195.80