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	$153.51	11.360%	$170.9487	$170.95	$170.95	$170.90
Purchase #2	$99.86	3.726%	$103.5808	$103.58	$103.60	$103.60
Purchase #3	$132.28	7.331%	$141.9774	$141.98	$142.00	$142.00
Purchase #4	$40.63	12.827%	$45.8416	$45.84	$45.85	$45.80
Purchase #5	$46.36	12.258%	$52.0428	$52.04	$52.05	$52.00
Purchase #6	$166.60	7.831%	$179.6464	$179.65	$179.65	$179.60
Purchase #7	$237.61	4.118%	$247.3948	$247.39	$247.40	$247.40
7 purchase totals =	$876.85		$941.4325	$941.43	$941.50	$941.30