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	$235.69	8.160%	$254.9223	$254.92	$254.90	$254.90
Purchase #2	$53.59	7.349%	$57.5283	$57.53	$57.55	$57.50
Purchase #3	$189.82	13.443%	$215.3375	$215.34	$215.35	$215.30
Purchase #4	$249.42	13.168%	$282.2636	$282.26	$282.25	$282.30
Purchase #5	$176.82	6.842%	$188.918	$188.92	$188.90	$188.90
Purchase #6	$160.50	13.119%	$181.556	$181.56	$181.55	$181.60
Purchase #7	$138.58	7.206%	$148.5661	$148.57	$148.55	$148.60
7 purchase totals =	$1,204.42		$1,329.0918	$1,329.10	$1,329.05	$1,329.10