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	$168.59	6.238%	$179.1066	$179.11	$179.10	$179.10
Purchase #2	$191.63	7.123%	$205.2798	$205.28	$205.30	$205.30
Purchase #3	$80.69	13.405%	$91.5065	$91.51	$91.50	$91.50
Purchase #4	$140.61	5.762%	$148.7119	$148.71	$148.70	$148.70
Purchase #5	$216.48	6.653%	$230.8824	$230.88	$230.90	$230.90
Purchase #6	$95.88	3.674%	$99.4026	$99.40	$99.40	$99.40
Purchase #7	$112.33	6.632%	$119.7797	$119.78	$119.80	$119.80
7 purchase totals =	$1,006.21		$1,074.6695	$1,074.67	$1,074.70	$1,074.70