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	$17.52	10.635%	$19.3833	$19.38	$19.40	$19.40
Purchase #2	$108.98	13.146%	$123.3065	$123.31	$123.30	$123.30
Purchase #3	$45.60	10.239%	$50.269	$50.27	$50.25	$50.30
Purchase #4	$151.85	7.221%	$162.8151	$162.82	$162.80	$162.80
Purchase #5	$242.42	3.498%	$250.8999	$250.90	$250.90	$250.90
Purchase #6	$191.43	10.848%	$212.1963	$212.20	$212.20	$212.20
Purchase #7	$198.37	3.293%	$204.9023	$204.90	$204.90	$204.90
7 purchase totals =	$956.17		$1,023.7724	$1,023.78	$1,023.75	$1,023.80