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	$41.53	10.536%	$45.9056	$45.91	$45.90	$45.90
Purchase #2	$105.59	5.780%	$111.6931	$111.69	$111.70	$111.70
Purchase #3	$81.89	9.586%	$89.74	$89.74	$89.75	$89.70
Purchase #4	$189.32	13.206%	$214.3216	$214.32	$214.30	$214.30
Purchase #5	$149.73	9.783%	$164.3781	$164.38	$164.40	$164.40
Purchase #6	$128.74	13.220%	$145.7594	$145.76	$145.75	$145.80
Purchase #7	$215.51	12.808%	$243.1125	$243.11	$243.10	$243.10
7 purchase totals =	$912.31		$1,014.9103	$1,014.91	$1,014.90	$1,014.90