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	$56.25	9.120%	$61.38	$61.38	$61.40	$61.40
Purchase #2	$217.57	12.196%	$244.1048	$244.10	$244.10	$244.10
Purchase #3	$7.30	3.745%	$7.5734	$7.57	$7.55	$7.60
Purchase #4	$49.95	12.158%	$56.0229	$56.02	$56.00	$56.00
Purchase #5	$214.90	11.865%	$240.3979	$240.40	$240.40	$240.40
Purchase #6	$157.66	9.393%	$172.469	$172.47	$172.45	$172.50
Purchase #7	$85.56	10.319%	$94.3889	$94.39	$94.40	$94.40
7 purchase totals =	$789.19		$876.3369	$876.33	$876.30	$876.40