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	$110.43	7.857%	$119.1065	$119.11	$119.10	$119.10
Purchase #2	$113.56	12.460%	$127.7096	$127.71	$127.70	$127.70
Purchase #3	$200.89	5.518%	$211.9751	$211.98	$212.00	$212.00
Purchase #4	$64.31	9.573%	$70.4664	$70.47	$70.45	$70.50
Purchase #5	$42.26	10.498%	$46.6965	$46.70	$46.70	$46.70
Purchase #6	$13.39	11.118%	$14.8787	$14.88	$14.90	$14.90
Purchase #7	$158.58	10.735%	$175.6036	$175.60	$175.60	$175.60
7 purchase totals =	$703.42		$766.4364	$766.45	$766.45	$766.50