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	$51.32	9.703%	$56.2996	$56.30	$56.30	$56.30
Purchase #2	$50.91	9.217%	$55.6024	$55.60	$55.60	$55.60
Purchase #3	$171.41	13.467%	$194.4938	$194.49	$194.50	$194.50
Purchase #4	$91.35	10.457%	$100.9025	$100.90	$100.90	$100.90
Purchase #5	$33.96	11.240%	$37.7771	$37.78	$37.80	$37.80
Purchase #6	$165.25	11.549%	$184.3347	$184.33	$184.35	$184.30
Purchase #7	$161.88	13.540%	$183.7986	$183.80	$183.80	$183.80
7 purchase totals =	$726.08		$813.2087	$813.20	$813.25	$813.20