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	$50.52	4.522%	$52.8045	$52.80	$52.80	$52.80
Purchase #2	$18.60	3.150%	$19.1859	$19.19	$19.20	$19.20
Purchase #3	$71.67	9.667%	$78.5983	$78.60	$78.60	$78.60
Purchase #4	$221.47	9.523%	$242.5606	$242.56	$242.55	$242.60
Purchase #5	$167.30	7.130%	$179.2285	$179.23	$179.25	$179.20
Purchase #6	$136.79	10.773%	$151.5264	$151.53	$151.55	$151.50
Purchase #7	$70.75	4.378%	$73.8474	$73.85	$73.85	$73.80
7 purchase totals =	$737.10		$797.7516	$797.76	$797.80	$797.70