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	$52.41	13.472%	$59.4707	$59.47	$59.45	$59.50
Purchase #2	$88.69	9.239%	$96.8841	$96.88	$96.90	$96.90
Purchase #3	$30.58	9.343%	$33.4371	$33.44	$33.45	$33.40
Purchase #4	$247.63	12.504%	$278.5937	$278.59	$278.60	$278.60
Purchase #5	$237.83	12.521%	$267.6087	$267.61	$267.60	$267.60
Purchase #6	$170.61	13.711%	$194.0023	$194.00	$194.00	$194.00
Purchase #7	$185.34	13.773%	$210.8669	$210.87	$210.85	$210.90
7 purchase totals =	$1,013.09		$1,140.8635	$1,140.86	$1,140.85	$1,140.90