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	$147.65	11.591%	$164.7641	$164.76	$164.75	$164.80
Purchase #2	$134.96	13.848%	$153.6493	$153.65	$153.65	$153.60
Purchase #3	$83.35	7.302%	$89.4362	$89.44	$89.45	$89.40
Purchase #4	$98.96	5.597%	$104.4988	$104.50	$104.50	$104.50
Purchase #5	$55.92	9.196%	$61.0624	$61.06	$61.05	$61.10
Purchase #6	$157.59	8.315%	$170.6936	$170.69	$170.70	$170.70
Purchase #7	$108.77	8.593%	$118.1166	$118.12	$118.10	$118.10
7 purchase totals =	$787.20		$862.2210	$862.22	$862.20	$862.20