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	$243.38	4.721%	$254.87	$254.87	$254.85	$254.90
Purchase #2	$87.44	13.822%	$99.526	$99.53	$99.55	$99.50
Purchase #3	$116.80	11.554%	$130.2951	$130.30	$130.30	$130.30
Purchase #4	$49.82	10.380%	$54.9913	$54.99	$55.00	$55.00
Purchase #5	$198.59	3.805%	$206.1463	$206.15	$206.15	$206.10
Purchase #6	$149.35	10.610%	$165.196	$165.20	$165.20	$165.20
Purchase #7	$245.54	9.626%	$269.1757	$269.18	$269.20	$269.20
7 purchase totals =	$1,090.92		$1,180.2004	$1,180.22	$1,180.25	$1,180.20