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	$43.34	5.768%	$45.8399	$45.84	$45.85	$45.80
Purchase #2	$80.93	10.256%	$89.2302	$89.23	$89.25	$89.20
Purchase #3	$72.32	7.735%	$77.914	$77.91	$77.90	$77.90
Purchase #4	$157.36	8.788%	$171.1888	$171.19	$171.20	$171.20
Purchase #5	$51.84	5.781%	$54.8369	$54.84	$54.85	$54.80
Purchase #6	$36.71	8.796%	$39.939	$39.94	$39.95	$39.90
Purchase #7	$193.29	9.754%	$212.1435	$212.14	$212.15	$212.10
7 purchase totals =	$635.79		$691.0923	$691.09	$691.15	$690.90