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	$64.69	10.694%	$71.6079	$71.61	$71.60	$71.60
Purchase #2	$108.33	8.569%	$117.6128	$117.61	$117.60	$117.60
Purchase #3	$6.91	7.289%	$7.4137	$7.41	$7.40	$7.40
Purchase #4	$174.33	4.805%	$182.7066	$182.71	$182.70	$182.70
Purchase #5	$230.50	7.386%	$247.5247	$247.52	$247.50	$247.50
Purchase #6	$59.74	12.751%	$67.3574	$67.36	$67.35	$67.40
Purchase #7	$151.79	9.483%	$166.1842	$166.18	$166.20	$166.20
7 purchase totals =	$796.29		$860.4073	$860.40	$860.35	$860.40