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	$215.25	7.164%	$230.6705	$230.67	$230.65	$230.70
Purchase #2	$65.53	10.236%	$72.2377	$72.24	$72.25	$72.20
Purchase #3	$177.31	3.676%	$183.8279	$183.83	$183.85	$183.80
Purchase #4	$250.34	7.656%	$269.506	$269.51	$269.50	$269.50
Purchase #5	$29.89	9.543%	$32.7424	$32.74	$32.75	$32.70
Purchase #6	$237.38	3.159%	$244.8788	$244.88	$244.90	$244.90
Purchase #7	$12.62	10.282%	$13.9176	$13.92	$13.90	$13.90
7 purchase totals =	$988.32		$1,047.7809	$1,047.79	$1,047.80	$1,047.70