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	$165.79	9.731%	$181.923	$181.92	$181.90	$181.90
Purchase #2	$45.33	10.622%	$50.145	$50.15	$50.15	$50.10
Purchase #3	$152.87	8.465%	$165.8104	$165.81	$165.80	$165.80
Purchase #4	$231.45	12.547%	$260.49	$260.49	$260.50	$260.50
Purchase #5	$29.42	4.820%	$30.838	$30.84	$30.85	$30.80
Purchase #6	$54.67	8.731%	$59.4432	$59.44	$59.45	$59.40
Purchase #7	$59.70	8.697%	$64.8921	$64.89	$64.90	$64.90
7 purchase totals =	$739.23		$813.5417	$813.54	$813.55	$813.40