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	$58.92	6.827%	$62.9425	$62.94	$62.95	$62.90
Purchase #2	$171.69	8.533%	$186.3403	$186.34	$186.35	$186.30
Purchase #3	$215.77	12.216%	$242.1285	$242.13	$242.15	$242.10
Purchase #4	$128.56	10.784%	$142.4239	$142.42	$142.40	$142.40
Purchase #5	$177.54	9.247%	$193.9571	$193.96	$193.95	$194.00
Purchase #6	$33.97	11.313%	$37.813	$37.81	$37.80	$37.80
Purchase #7	$81.72	9.620%	$89.5815	$89.58	$89.60	$89.60
7 purchase totals =	$868.17		$955.1868	$955.18	$955.20	$955.10