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	$58.75	9.584%	$64.3806	$64.38	$64.40	$64.40
Purchase #2	$191.82	11.472%	$213.8256	$213.83	$213.85	$213.80
Purchase #3	$162.53	6.679%	$173.3854	$173.39	$173.40	$173.40
Purchase #4	$10.84	13.536%	$12.3073	$12.31	$12.30	$12.30
Purchase #5	$229.34	11.243%	$255.1247	$255.12	$255.10	$255.10
Purchase #6	$205.84	9.567%	$225.5327	$225.53	$225.55	$225.50
Purchase #7	$220.44	10.540%	$243.6744	$243.67	$243.65	$243.70
7 purchase totals =	$1,079.56		$1,188.2307	$1,188.23	$1,188.25	$1,188.20