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	$131.69	10.293%	$145.2449	$145.24	$145.25	$145.20
Purchase #2	$22.39	8.346%	$24.2587	$24.26	$24.25	$24.30
Purchase #3	$199.89	6.274%	$212.4311	$212.43	$212.45	$212.40
Purchase #4	$91.48	4.130%	$95.2581	$95.26	$95.25	$95.30
Purchase #5	$17.77	9.196%	$19.4041	$19.40	$19.40	$19.40
Purchase #6	$10.36	11.533%	$11.5548	$11.55	$11.55	$11.60
Purchase #7	$88.30	12.631%	$99.4532	$99.45	$99.45	$99.50
7 purchase totals =	$561.88		$607.6049	$607.59	$607.60	$607.70