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	$230.58	13.437%	$261.563	$261.56	$261.55	$261.60
Purchase #2	$226.58	12.744%	$255.4554	$255.46	$255.45	$255.50
Purchase #3	$127.48	10.636%	$141.0388	$141.04	$141.05	$141.00
Purchase #4	$85.46	12.104%	$95.8041	$95.80	$95.80	$95.80
Purchase #5	$36.96	10.273%	$40.7569	$40.76	$40.75	$40.80
Purchase #6	$209.29	4.331%	$218.3543	$218.35	$218.35	$218.40
Purchase #7	$118.43	11.261%	$131.7664	$131.77	$131.75	$131.80
7 purchase totals =	$1,034.78		$1,144.7389	$1,144.74	$1,144.70	$1,144.90