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	$84.31	7.614%	$90.7294	$90.73	$90.75	$90.70
Purchase #2	$47.28	9.578%	$51.8085	$51.81	$51.80	$51.80
Purchase #3	$54.46	6.802%	$58.1644	$58.16	$58.15	$58.20
Purchase #4	$171.35	11.372%	$190.8359	$190.84	$190.85	$190.80
Purchase #5	$153.85	8.697%	$167.2303	$167.23	$167.25	$167.20
Purchase #6	$196.59	10.488%	$217.2084	$217.21	$217.20	$217.20
Purchase #7	$250.48	8.733%	$272.3544	$272.35	$272.35	$272.40
7 purchase totals =	$958.32		$1,048.3313	$1,048.33	$1,048.35	$1,048.30