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	$125.81	5.655%	$132.9246	$132.92	$132.90	$132.90
Purchase #2	$58.36	5.525%	$61.5844	$61.58	$61.60	$61.60
Purchase #3	$61.78	6.165%	$65.5887	$65.59	$65.60	$65.60
Purchase #4	$242.33	7.198%	$259.7729	$259.77	$259.75	$259.80
Purchase #5	$92.66	3.759%	$96.1431	$96.14	$96.15	$96.10
Purchase #6	$85.56	11.480%	$95.3823	$95.38	$95.40	$95.40
Purchase #7	$201.72	8.826%	$219.5238	$219.52	$219.50	$219.50
7 purchase totals =	$868.22		$930.9198	$930.90	$930.90	$930.90