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	$188.42	3.147%	$194.3496	$194.35	$194.35	$194.30
Purchase #2	$65.32	7.211%	$70.0302	$70.03	$70.05	$70.00
Purchase #3	$226.45	11.481%	$252.4487	$252.45	$252.45	$252.40
Purchase #4	$68.60	5.144%	$72.1288	$72.13	$72.15	$72.10
Purchase #5	$101.94	10.241%	$112.3797	$112.38	$112.40	$112.40
Purchase #6	$84.89	6.284%	$90.2245	$90.22	$90.20	$90.20
Purchase #7	$155.33	11.737%	$173.5611	$173.56	$173.55	$173.60
7 purchase totals =	$890.95		$965.1226	$965.12	$965.15	$965.00