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	$164.46	4.511%	$171.8788	$171.88	$171.90	$171.90
Purchase #2	$132.74	9.363%	$145.1684	$145.17	$145.15	$145.20
Purchase #3	$85.47	3.144%	$88.1572	$88.16	$88.15	$88.20
Purchase #4	$169.66	7.626%	$182.5983	$182.60	$182.60	$182.60
Purchase #5	$215.61	6.872%	$230.4267	$230.43	$230.45	$230.40
Purchase #6	$200.92	7.819%	$216.6299	$216.63	$216.65	$216.60
Purchase #7	$175.73	13.539%	$199.5221	$199.52	$199.50	$199.50
7 purchase totals =	$1,144.59		$1,234.3814	$1,234.39	$1,234.40	$1,234.40