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	$169.70	9.833%	$186.3866	$186.39	$186.40	$186.40
Purchase #2	$178.25	10.123%	$196.2942	$196.29	$196.30	$196.30
Purchase #3	$87.51	10.303%	$96.5262	$96.53	$96.55	$96.50
Purchase #4	$26.39	8.672%	$28.6785	$28.68	$28.70	$28.70
Purchase #5	$79.86	11.826%	$89.3042	$89.30	$89.30	$89.30
Purchase #6	$48.72	9.138%	$53.172	$53.17	$53.15	$53.20
Purchase #7	$103.69	11.789%	$115.914	$115.91	$115.90	$115.90
7 purchase totals =	$694.12		$766.2757	$766.27	$766.30	$766.30