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	$39.32	13.246%	$44.5283	$44.53	$44.55	$44.50
Purchase #2	$139.50	6.673%	$148.8088	$148.81	$148.80	$148.80
Purchase #3	$90.69	3.591%	$93.9467	$93.95	$93.95	$93.90
Purchase #4	$222.39	12.474%	$250.1309	$250.13	$250.15	$250.10
Purchase #5	$78.77	9.538%	$86.2831	$86.28	$86.30	$86.30
Purchase #6	$151.29	13.661%	$171.9577	$171.96	$171.95	$172.00
Purchase #7	$183.90	12.592%	$207.0567	$207.06	$207.05	$207.10
7 purchase totals =	$905.86		$1,002.7122	$1,002.72	$1,002.75	$1,002.70