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	$246.38	7.293%	$264.3485	$264.35	$264.35	$264.30
Purchase #2	$95.43	4.532%	$99.7549	$99.75	$99.75	$99.80
Purchase #3	$162.37	6.284%	$172.5733	$172.57	$172.55	$172.60
Purchase #4	$102.87	4.136%	$107.1247	$107.12	$107.10	$107.10
Purchase #5	$105.34	11.371%	$117.3182	$117.32	$117.30	$117.30
Purchase #6	$101.46	3.745%	$105.2597	$105.26	$105.25	$105.30
Purchase #7	$153.93	8.480%	$166.9833	$166.98	$167.00	$167.00
7 purchase totals =	$967.78		$1,033.3626	$1,033.35	$1,033.30	$1,033.40