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	$122.34	9.172%	$133.561	$133.56	$133.55	$133.60
Purchase #2	$219.47	4.298%	$228.9028	$228.90	$228.90	$228.90
Purchase #3	$89.97	10.489%	$99.407	$99.41	$99.40	$99.40
Purchase #4	$9.91	7.256%	$10.6291	$10.63	$10.65	$10.60
Purchase #5	$72.78	13.555%	$82.6453	$82.65	$82.65	$82.60
Purchase #6	$201.27	5.616%	$212.5733	$212.57	$212.55	$212.60
Purchase #7	$210.84	13.490%	$239.2823	$239.28	$239.30	$239.30
7 purchase totals =	$926.58		$1,007.0008	$1,007.00	$1,007.00	$1,007.00