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	$100.31	5.138%	$105.4639	$105.46	$105.45	$105.50
Purchase #2	$60.72	10.116%	$66.8624	$66.86	$66.85	$66.90
Purchase #3	$155.58	10.528%	$171.9595	$171.96	$171.95	$172.00
Purchase #4	$62.37	13.317%	$70.6758	$70.68	$70.70	$70.70
Purchase #5	$234.97	12.738%	$264.9005	$264.90	$264.90	$264.90
Purchase #6	$214.76	13.498%	$243.7483	$243.75	$243.75	$243.70
Purchase #7	$80.85	6.581%	$86.1707	$86.17	$86.15	$86.20
7 purchase totals =	$909.56		$1,009.7811	$1,009.78	$1,009.75	$1,009.90