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	$42.55	8.289%	$46.077	$46.08	$46.10	$46.10
Purchase #2	$94.85	8.634%	$103.0393	$103.04	$103.05	$103.00
Purchase #3	$244.95	5.629%	$258.7382	$258.74	$258.75	$258.70
Purchase #4	$220.55	10.740%	$244.2371	$244.24	$244.25	$244.20
Purchase #5	$170.46	11.217%	$189.5805	$189.58	$189.60	$189.60
Purchase #6	$35.67	13.420%	$40.4569	$40.46	$40.45	$40.50
Purchase #7	$107.98	3.644%	$111.9148	$111.91	$111.90	$111.90
7 purchase totals =	$917.01		$994.0438	$994.05	$994.10	$994.00