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	$84.26	6.183%	$89.4698	$89.47	$89.45	$89.50
Purchase #2	$74.71	11.722%	$83.4675	$83.47	$83.45	$83.50
Purchase #3	$55.71	5.461%	$58.7523	$58.75	$58.75	$58.80
Purchase #4	$248.71	6.578%	$265.0701	$265.07	$265.05	$265.10
Purchase #5	$235.38	3.560%	$243.7595	$243.76	$243.75	$243.80
Purchase #6	$181.50	3.642%	$188.1102	$188.11	$188.10	$188.10
Purchase #7	$129.54	4.164%	$134.934	$134.93	$134.95	$134.90
7 purchase totals =	$1,009.81		$1,063.5634	$1,063.56	$1,063.50	$1,063.70