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	$124.89	5.187%	$131.368	$131.37	$131.35	$131.40
Purchase #2	$215.46	3.828%	$223.7078	$223.71	$223.70	$223.70
Purchase #3	$59.28	6.775%	$63.2962	$63.30	$63.30	$63.30
Purchase #4	$245.60	12.272%	$275.74	$275.74	$275.75	$275.70
Purchase #5	$96.89	7.617%	$104.2701	$104.27	$104.25	$104.30
Purchase #6	$88.25	10.396%	$97.4245	$97.42	$97.40	$97.40
Purchase #7	$96.49	5.309%	$101.6127	$101.61	$101.60	$101.60
7 purchase totals =	$926.86		$997.4193	$997.42	$997.35	$997.40