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	$89.49	13.500%	$101.5712	$101.57	$101.55	$101.60
Purchase #2	$48.78	3.362%	$50.42	$50.42	$50.40	$50.40
Purchase #3	$39.44	7.679%	$42.4686	$42.47	$42.45	$42.50
Purchase #4	$93.99	10.545%	$103.9012	$103.90	$103.90	$103.90
Purchase #5	$170.82	7.513%	$183.6537	$183.65	$183.65	$183.70
Purchase #6	$58.42	3.153%	$60.262	$60.26	$60.25	$60.30
Purchase #7	$134.37	12.213%	$150.7806	$150.78	$150.80	$150.80
7 purchase totals =	$635.31		$693.0573	$693.05	$693.00	$693.20