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	$207.34	11.463%	$231.1074	$231.11	$231.10	$231.10
Purchase #2	$43.91	6.485%	$46.7576	$46.76	$46.75	$46.80
Purchase #3	$79.71	13.550%	$90.5107	$90.51	$90.50	$90.50
Purchase #4	$173.73	10.550%	$192.0585	$192.06	$192.05	$192.10
Purchase #5	$59.46	3.156%	$61.3366	$61.34	$61.35	$61.30
Purchase #6	$231.58	10.121%	$255.0182	$255.02	$255.00	$255.00
Purchase #7	$73.60	10.133%	$81.0579	$81.06	$81.05	$81.10
7 purchase totals =	$869.33		$957.8469	$957.86	$957.80	$957.90