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	$209.31	9.623%	$229.4519	$229.45	$229.45	$229.50
Purchase #2	$243.89	12.698%	$274.8592	$274.86	$274.85	$274.90
Purchase #3	$54.58	12.563%	$61.4369	$61.44	$61.45	$61.40
Purchase #4	$60.59	11.171%	$67.3585	$67.36	$67.35	$67.40
Purchase #5	$119.77	9.772%	$131.4739	$131.47	$131.45	$131.50
Purchase #6	$158.66	5.121%	$166.785	$166.79	$166.80	$166.80
Purchase #7	$197.92	5.236%	$208.2831	$208.28	$208.30	$208.30
7 purchase totals =	$1,044.72		$1,139.6485	$1,139.65	$1,139.65	$1,139.80