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	$220.79	7.669%	$237.7224	$237.72	$237.70	$237.70
Purchase #2	$89.57	8.145%	$96.8655	$96.87	$96.85	$96.90
Purchase #3	$207.70	11.282%	$231.1327	$231.13	$231.15	$231.10
Purchase #4	$6.86	8.304%	$7.4297	$7.43	$7.45	$7.40
Purchase #5	$158.84	5.364%	$167.3602	$167.36	$167.35	$167.40
Purchase #6	$185.83	12.621%	$209.2836	$209.28	$209.30	$209.30
Purchase #7	$59.31	12.569%	$66.7647	$66.76	$66.75	$66.80
7 purchase totals =	$928.90		$1,016.5588	$1,016.55	$1,016.55	$1,016.60