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	$205.94	12.623%	$231.9358	$231.94	$231.95	$231.90
Purchase #2	$150.31	5.298%	$158.2734	$158.27	$158.25	$158.30
Purchase #3	$103.75	5.573%	$109.532	$109.53	$109.55	$109.50
Purchase #4	$79.26	13.827%	$90.2193	$90.22	$90.20	$90.20
Purchase #5	$168.98	12.680%	$190.4067	$190.41	$190.40	$190.40
Purchase #6	$28.31	4.272%	$29.5194	$29.52	$29.50	$29.50
Purchase #7	$218.51	10.855%	$242.2293	$242.23	$242.25	$242.20
7 purchase totals =	$955.06		$1,052.1159	$1,052.12	$1,052.10	$1,052.00