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	$41.53	3.561%	$43.0089	$43.01	$43.00	$43.00
Purchase #2	$70.91	13.601%	$80.5545	$80.55	$80.55	$80.60
Purchase #3	$248.85	7.737%	$268.1035	$268.10	$268.10	$268.10
Purchase #4	$229.33	10.456%	$253.3087	$253.31	$253.30	$253.30
Purchase #5	$69.88	10.803%	$77.4291	$77.43	$77.45	$77.40
Purchase #6	$211.52	5.151%	$222.4154	$222.42	$222.40	$222.40
Purchase #7	$75.31	13.495%	$85.4731	$85.47	$85.45	$85.50
7 purchase totals =	$947.33		$1,030.2932	$1,030.29	$1,030.25	$1,030.30