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	$35.52	4.399%	$37.0825	$37.08	$37.10	$37.10
Purchase #2	$53.82	6.349%	$57.237	$57.24	$57.25	$57.20
Purchase #3	$113.88	11.534%	$127.0149	$127.01	$127.00	$127.00
Purchase #4	$60.43	7.273%	$64.8251	$64.83	$64.85	$64.80
Purchase #5	$125.34	5.713%	$132.5007	$132.50	$132.50	$132.50
Purchase #6	$110.60	3.726%	$114.721	$114.72	$114.70	$114.70
Purchase #7	$131.28	11.461%	$146.326	$146.33	$146.35	$146.30
7 purchase totals =	$630.87		$679.7072	$679.71	$679.75	$679.60