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	$150.27	9.373%	$164.3548	$164.35	$164.35	$164.40
Purchase #2	$68.56	4.836%	$71.8756	$71.88	$71.90	$71.90
Purchase #3	$65.62	12.438%	$73.7818	$73.78	$73.80	$73.80
Purchase #4	$120.86	4.419%	$126.2008	$126.20	$126.20	$126.20
Purchase #5	$158.41	4.562%	$165.6367	$165.64	$165.65	$165.60
Purchase #6	$30.51	7.436%	$32.7787	$32.78	$32.80	$32.80
Purchase #7	$96.66	7.520%	$103.9288	$103.93	$103.95	$103.90
7 purchase totals =	$690.89		$738.5572	$738.56	$738.65	$738.60