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	$118.40	11.283%	$131.7591	$131.76	$131.75	$131.80
Purchase #2	$164.96	8.593%	$179.135	$179.14	$179.15	$179.10
Purchase #3	$148.96	12.390%	$167.4161	$167.42	$167.40	$167.40
Purchase #4	$12.31	7.407%	$13.2218	$13.22	$13.20	$13.20
Purchase #5	$187.83	11.841%	$210.071	$210.07	$210.05	$210.10
Purchase #6	$139.25	6.515%	$148.3221	$148.32	$148.30	$148.30
Purchase #7	$225.95	8.612%	$245.4088	$245.41	$245.40	$245.40
7 purchase totals =	$997.66		$1,095.3339	$1,095.34	$1,095.25	$1,095.30