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	$32.51	3.326%	$33.5913	$33.59	$33.60	$33.60
Purchase #2	$19.84	11.409%	$22.1035	$22.10	$22.10	$22.10
Purchase #3	$128.95	4.345%	$134.5529	$134.55	$134.55	$134.60
Purchase #4	$151.56	5.764%	$160.2959	$160.30	$160.30	$160.30
Purchase #5	$74.86	3.586%	$77.5445	$77.54	$77.55	$77.50
Purchase #6	$170.73	6.755%	$182.2628	$182.26	$182.25	$182.30
Purchase #7	$162.28	6.685%	$173.1284	$173.13	$173.15	$173.10
7 purchase totals =	$740.73		$783.4793	$783.47	$783.50	$783.50