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	$184.88	13.212%	$209.3063	$209.31	$209.30	$209.30
Purchase #2	$11.38	13.499%	$12.9162	$12.92	$12.90	$12.90
Purchase #3	$158.57	8.830%	$172.5717	$172.57	$172.55	$172.60
Purchase #4	$46.86	8.483%	$50.8351	$50.84	$50.85	$50.80
Purchase #5	$148.96	13.297%	$168.7672	$168.77	$168.75	$168.80
Purchase #6	$99.98	5.644%	$105.6229	$105.62	$105.60	$105.60
Purchase #7	$237.66	8.476%	$257.8041	$257.80	$257.80	$257.80
7 purchase totals =	$888.29		$977.8235	$977.83	$977.75	$977.80