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	$49.49	10.740%	$54.8052	$54.81	$54.80	$54.80
Purchase #2	$139.51	3.551%	$144.464	$144.46	$144.45	$144.50
Purchase #3	$47.37	10.609%	$52.3955	$52.40	$52.40	$52.40
Purchase #4	$244.27	7.651%	$262.9591	$262.96	$262.95	$263.00
Purchase #5	$238.61	8.261%	$258.3216	$258.32	$258.30	$258.30
Purchase #6	$70.95	9.776%	$77.8861	$77.89	$77.90	$77.90
Purchase #7	$205.96	8.463%	$223.3904	$223.39	$223.40	$223.40
7 purchase totals =	$996.16		$1,074.2219	$1,074.23	$1,074.20	$1,074.30