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	$192.80	10.620%	$213.2754	$213.28	$213.30	$213.30
Purchase #2	$216.94	13.187%	$245.5479	$245.55	$245.55	$245.50
Purchase #3	$198.68	5.347%	$209.3034	$209.30	$209.30	$209.30
Purchase #4	$73.72	12.507%	$82.9402	$82.94	$82.95	$82.90
Purchase #5	$39.63	6.696%	$42.2836	$42.28	$42.30	$42.30
Purchase #6	$227.54	12.519%	$256.0257	$256.03	$256.05	$256.00
Purchase #7	$130.76	4.392%	$136.503	$136.50	$136.50	$136.50
7 purchase totals =	$1,080.07		$1,185.8792	$1,185.88	$1,185.95	$1,185.80