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	$139.68	6.287%	$148.4617	$148.46	$148.45	$148.50
Purchase #2	$193.90	4.145%	$201.9372	$201.94	$201.95	$201.90
Purchase #3	$25.72	6.224%	$27.3208	$27.32	$27.30	$27.30
Purchase #4	$199.91	5.444%	$210.7931	$210.79	$210.80	$210.80
Purchase #5	$64.25	3.322%	$66.3844	$66.38	$66.40	$66.40
Purchase #6	$92.51	7.282%	$99.2466	$99.25	$99.25	$99.20
Purchase #7	$170.98	4.873%	$179.3119	$179.31	$179.30	$179.30
7 purchase totals =	$886.95		$933.4557	$933.45	$933.45	$933.40