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	$103.94	3.391%	$107.4646	$107.46	$107.45	$107.50
Purchase #2	$210.60	9.142%	$229.8531	$229.85	$229.85	$229.90
Purchase #3	$206.90	7.536%	$222.492	$222.49	$222.50	$222.50
Purchase #4	$161.98	6.784%	$172.9687	$172.97	$172.95	$173.00
Purchase #5	$90.52	6.755%	$96.6346	$96.63	$96.65	$96.60
Purchase #6	$131.67	11.816%	$147.2281	$147.23	$147.25	$147.20
Purchase #7	$67.59	7.544%	$72.689	$72.69	$72.70	$72.70
7 purchase totals =	$973.20		$1,049.3301	$1,049.32	$1,049.35	$1,049.40