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	$147.59	12.620%	$166.2159	$166.22	$166.20	$166.20
Purchase #2	$11.41	12.826%	$12.8734	$12.87	$12.85	$12.90
Purchase #3	$9.30	7.702%	$10.0163	$10.02	$10.00	$10.00
Purchase #4	$156.27	3.709%	$162.0661	$162.07	$162.05	$162.10
Purchase #5	$244.34	3.608%	$253.1558	$253.16	$253.15	$253.20
Purchase #6	$62.95	13.395%	$71.3822	$71.38	$71.40	$71.40
Purchase #7	$33.51	11.296%	$37.2953	$37.30	$37.30	$37.30
7 purchase totals =	$665.37		$713.0050	$713.02	$712.95	$713.10