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	$197.56	12.280%	$221.8204	$221.82	$221.80	$221.80
Purchase #2	$157.25	7.391%	$168.8723	$168.87	$168.85	$168.90
Purchase #3	$120.93	5.476%	$127.5521	$127.55	$127.55	$127.60
Purchase #4	$106.31	4.574%	$111.1726	$111.17	$111.15	$111.20
Purchase #5	$185.62	4.173%	$193.3659	$193.37	$193.35	$193.40
Purchase #6	$149.47	8.637%	$162.3797	$162.38	$162.40	$162.40
Purchase #7	$157.74	4.797%	$165.3068	$165.31	$165.30	$165.30
7 purchase totals =	$1,074.88		$1,150.4698	$1,150.47	$1,150.40	$1,150.60