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	$90.27	7.270%	$96.8326	$96.83	$96.85	$96.80
Purchase #2	$141.32	7.354%	$151.7127	$151.71	$151.70	$151.70
Purchase #3	$92.89	11.192%	$103.2862	$103.29	$103.30	$103.30
Purchase #4	$161.72	3.814%	$167.888	$167.89	$167.90	$167.90
Purchase #5	$108.57	10.589%	$120.0665	$120.07	$120.05	$120.10
Purchase #6	$186.51	9.806%	$204.7992	$204.80	$204.80	$204.80
Purchase #7	$32.38	9.125%	$35.3347	$35.33	$35.35	$35.30
7 purchase totals =	$813.66		$879.9199	$879.92	$879.95	$879.90