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	$227.78	7.612%	$245.1186	$245.12	$245.10	$245.10
Purchase #2	$79.82	3.587%	$82.6831	$82.68	$82.70	$82.70
Purchase #3	$74.96	8.206%	$81.1112	$81.11	$81.10	$81.10
Purchase #4	$68.89	13.507%	$78.195	$78.20	$78.20	$78.20
Purchase #5	$200.71	5.514%	$211.7771	$211.78	$211.80	$211.80
Purchase #6	$239.82	3.671%	$248.6238	$248.62	$248.60	$248.60
Purchase #7	$63.33	13.568%	$71.9226	$71.92	$71.90	$71.90
7 purchase totals =	$955.31		$1,019.4314	$1,019.43	$1,019.40	$1,019.40