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	$151.73	13.375%	$172.0239	$172.02	$172.00	$172.00
Purchase #2	$248.32	4.392%	$259.2262	$259.23	$259.25	$259.20
Purchase #3	$229.27	5.474%	$241.8202	$241.82	$241.80	$241.80
Purchase #4	$121.38	5.356%	$127.8811	$127.88	$127.90	$127.90
Purchase #5	$30.87	12.564%	$34.7485	$34.75	$34.75	$34.70
Purchase #6	$91.74	6.711%	$97.8967	$97.90	$97.90	$97.90
Purchase #7	$62.74	11.852%	$70.1759	$70.18	$70.20	$70.20
7 purchase totals =	$936.05		$1,003.7725	$1,003.78	$1,003.80	$1,003.70