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	$16.63	7.355%	$17.8531	$17.85	$17.85	$17.90
Purchase #2	$57.88	5.422%	$61.0183	$61.02	$61.00	$61.00
Purchase #3	$81.53	13.492%	$92.53	$92.53	$92.55	$92.50
Purchase #4	$230.83	8.398%	$250.2151	$250.22	$250.20	$250.20
Purchase #5	$164.71	13.379%	$186.7466	$186.75	$186.75	$186.70
Purchase #6	$61.36	5.792%	$64.914	$64.91	$64.90	$64.90
Purchase #7	$81.34	10.158%	$89.6025	$89.60	$89.60	$89.60
7 purchase totals =	$694.28		$762.8796	$762.88	$762.85	$762.80