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	$199.84	4.478%	$208.7888	$208.79	$208.80	$208.80
Purchase #2	$165.50	13.164%	$187.2864	$187.29	$187.30	$187.30
Purchase #3	$5.33	10.813%	$5.9063	$5.91	$5.90	$5.90
Purchase #4	$42.42	11.595%	$47.3386	$47.34	$47.35	$47.30
Purchase #5	$72.86	8.196%	$78.8316	$78.83	$78.85	$78.80
Purchase #6	$212.82	7.817%	$229.4561	$229.46	$229.45	$229.50
Purchase #7	$31.94	12.573%	$35.9558	$35.96	$35.95	$36.00
7 purchase totals =	$730.71		$793.5636	$793.58	$793.60	$793.60