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	$126.89	11.155%	$141.0446	$141.04	$141.05	$141.00
Purchase #2	$153.65	3.247%	$158.639	$158.64	$158.65	$158.60
Purchase #3	$113.37	13.649%	$128.8439	$128.84	$128.85	$128.80
Purchase #4	$73.37	9.111%	$80.0547	$80.05	$80.05	$80.10
Purchase #5	$11.83	3.476%	$12.2412	$12.24	$12.25	$12.20
Purchase #6	$155.86	6.545%	$166.061	$166.06	$166.05	$166.10
Purchase #7	$36.56	13.289%	$41.4185	$41.42	$41.40	$41.40
7 purchase totals =	$671.53		$728.3029	$728.29	$728.30	$728.20