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	$92.96	8.408%	$100.7761	$100.78	$100.80	$100.80
Purchase #2	$99.42	4.668%	$104.0609	$104.06	$104.05	$104.10
Purchase #3	$232.70	7.673%	$250.5551	$250.56	$250.55	$250.60
Purchase #4	$236.81	9.754%	$259.9084	$259.91	$259.90	$259.90
Purchase #5	$25.32	5.170%	$26.629	$26.63	$26.65	$26.60
Purchase #6	$162.68	9.345%	$177.8824	$177.88	$177.90	$177.90
Purchase #7	$77.42	6.698%	$82.6056	$82.61	$82.60	$82.60
7 purchase totals =	$927.31		$1,002.4175	$1,002.43	$1,002.45	$1,002.50