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	$181.57	9.119%	$198.1274	$198.13	$198.15	$198.10
Purchase #2	$163.44	13.700%	$185.8313	$185.83	$185.85	$185.80
Purchase #3	$67.89	6.655%	$72.4081	$72.41	$72.40	$72.40
Purchase #4	$211.35	9.217%	$230.8301	$230.83	$230.85	$230.80
Purchase #5	$38.79	8.678%	$42.1562	$42.16	$42.15	$42.20
Purchase #6	$171.39	6.255%	$182.1104	$182.11	$182.10	$182.10
Purchase #7	$248.85	3.146%	$256.6788	$256.68	$256.70	$256.70
7 purchase totals =	$1,083.28		$1,168.1423	$1,168.15	$1,168.20	$1,168.10