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	$158.38	5.772%	$167.5217	$167.52	$167.50	$167.50
Purchase #2	$80.65	10.446%	$89.0747	$89.07	$89.05	$89.10
Purchase #3	$214.62	9.819%	$235.6935	$235.69	$235.70	$235.70
Purchase #4	$112.90	6.198%	$119.8975	$119.90	$119.90	$119.90
Purchase #5	$85.50	4.605%	$89.4373	$89.44	$89.45	$89.40
Purchase #6	$129.91	9.197%	$141.8578	$141.86	$141.85	$141.90
Purchase #7	$165.93	13.370%	$188.1148	$188.11	$188.10	$188.10
7 purchase totals =	$947.89		$1,031.5973	$1,031.59	$1,031.55	$1,031.60