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	$148.71	13.857%	$169.3167	$169.32	$169.30	$169.30
Purchase #2	$166.91	7.339%	$179.1595	$179.16	$179.15	$179.20
Purchase #3	$232.26	5.636%	$245.3502	$245.35	$245.35	$245.40
Purchase #4	$164.51	5.435%	$173.4511	$173.45	$173.45	$173.50
Purchase #5	$52.27	3.187%	$53.9358	$53.94	$53.95	$53.90
Purchase #6	$17.80	5.753%	$18.824	$18.82	$18.80	$18.80
Purchase #7	$149.27	10.255%	$164.5776	$164.58	$164.60	$164.60
7 purchase totals =	$931.73		$1,004.6149	$1,004.62	$1,004.60	$1,004.70