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	$148.38	11.148%	$164.9214	$164.92	$164.90	$164.90
Purchase #2	$98.56	6.388%	$104.856	$104.86	$104.85	$104.90
Purchase #3	$241.30	9.768%	$264.8702	$264.87	$264.85	$264.90
Purchase #4	$146.33	10.758%	$162.0722	$162.07	$162.05	$162.10
Purchase #5	$115.76	13.380%	$131.2487	$131.25	$131.25	$131.20
Purchase #6	$32.86	11.775%	$36.7293	$36.73	$36.75	$36.70
Purchase #7	$224.58	8.416%	$243.4807	$243.48	$243.50	$243.50
7 purchase totals =	$1,007.77		$1,108.1785	$1,108.18	$1,108.15	$1,108.20