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	$96.73	13.805%	$110.0836	$110.08	$110.10	$110.10
Purchase #2	$70.76	11.385%	$78.816	$78.82	$78.80	$78.80
Purchase #3	$185.97	9.754%	$204.1095	$204.11	$204.10	$204.10
Purchase #4	$146.67	12.693%	$165.2868	$165.29	$165.30	$165.30
Purchase #5	$74.88	7.406%	$80.4256	$80.43	$80.45	$80.40
Purchase #6	$211.56	5.437%	$223.0625	$223.06	$223.05	$223.10
Purchase #7	$146.83	9.227%	$160.378	$160.38	$160.40	$160.40
7 purchase totals =	$933.40		$1,022.1620	$1,022.17	$1,022.20	$1,022.20