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	$53.56	9.239%	$58.5084	$58.51	$58.50	$58.50
Purchase #2	$185.25	5.843%	$196.0742	$196.07	$196.05	$196.10
Purchase #3	$212.32	4.521%	$221.919	$221.92	$221.90	$221.90
Purchase #4	$139.61	9.571%	$152.9721	$152.97	$152.95	$153.00
Purchase #5	$44.98	9.202%	$49.1191	$49.12	$49.10	$49.10
Purchase #6	$186.61	5.221%	$196.3529	$196.35	$196.35	$196.40
Purchase #7	$225.77	7.794%	$243.3665	$243.37	$243.35	$243.40
7 purchase totals =	$1,048.10		$1,118.3122	$1,118.31	$1,118.20	$1,118.40