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	$215.81	4.275%	$225.0359	$225.04	$225.05	$225.00
Purchase #2	$240.74	9.445%	$263.4779	$263.48	$263.50	$263.50
Purchase #3	$98.98	4.285%	$103.2213	$103.22	$103.20	$103.20
Purchase #4	$89.90	7.723%	$96.843	$96.84	$96.85	$96.80
Purchase #5	$59.66	11.618%	$66.5913	$66.59	$66.60	$66.60
Purchase #6	$55.50	10.407%	$61.2759	$61.28	$61.30	$61.30
Purchase #7	$34.85	4.470%	$36.4078	$36.41	$36.40	$36.40
7 purchase totals =	$795.44		$852.8531	$852.86	$852.90	$852.80