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	$137.74	10.183%	$151.7661	$151.77	$151.75	$151.80
Purchase #2	$134.91	4.545%	$141.0417	$141.04	$141.05	$141.00
Purchase #3	$64.43	10.463%	$71.1713	$71.17	$71.15	$71.20
Purchase #4	$120.47	9.230%	$131.5894	$131.59	$131.60	$131.60
Purchase #5	$75.37	7.120%	$80.7363	$80.74	$80.75	$80.70
Purchase #6	$177.47	5.851%	$187.8538	$187.85	$187.85	$187.90
Purchase #7	$169.89	6.749%	$181.3559	$181.36	$181.35	$181.40
7 purchase totals =	$880.28		$945.5145	$945.52	$945.50	$945.60