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	$104.80	4.443%	$109.4563	$109.46	$109.45	$109.50
Purchase #2	$139.83	10.160%	$154.0367	$154.04	$154.05	$154.00
Purchase #3	$21.83	11.332%	$24.3038	$24.30	$24.30	$24.30
Purchase #4	$80.89	10.434%	$89.3301	$89.33	$89.35	$89.30
Purchase #5	$197.71	7.615%	$212.7656	$212.77	$212.75	$212.80
Purchase #6	$74.99	4.413%	$78.2993	$78.30	$78.30	$78.30
Purchase #7	$228.42	8.468%	$247.7626	$247.76	$247.75	$247.80
7 purchase totals =	$848.47		$915.9544	$915.96	$915.95	$916.00