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	$173.85	5.147%	$182.7981	$182.80	$182.80	$182.80
Purchase #2	$150.45	5.307%	$158.4344	$158.43	$158.45	$158.40
Purchase #3	$172.75	7.328%	$185.4091	$185.41	$185.40	$185.40
Purchase #4	$135.99	12.625%	$153.1587	$153.16	$153.15	$153.20
Purchase #5	$158.64	10.594%	$175.4463	$175.45	$175.45	$175.40
Purchase #6	$242.34	12.731%	$273.1923	$273.19	$273.20	$273.20
Purchase #7	$39.28	11.686%	$43.8703	$43.87	$43.85	$43.90
7 purchase totals =	$1,073.30		$1,172.3092	$1,172.31	$1,172.30	$1,172.30