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	$6.52	8.632%	$7.0828	$7.08	$7.10	$7.10
Purchase #2	$53.94	13.754%	$61.3589	$61.36	$61.35	$61.40
Purchase #3	$78.78	8.501%	$85.4771	$85.48	$85.50	$85.50
Purchase #4	$84.31	11.796%	$94.2552	$94.26	$94.25	$94.30
Purchase #5	$160.45	13.628%	$182.3161	$182.32	$182.30	$182.30
Purchase #6	$155.90	12.180%	$174.8886	$174.89	$174.90	$174.90
Purchase #7	$116.57	7.269%	$125.0435	$125.04	$125.05	$125.00
7 purchase totals =	$656.47		$730.4222	$730.43	$730.45	$730.50