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	$132.58	6.187%	$140.7827	$140.78	$140.80	$140.80
Purchase #2	$16.56	10.431%	$18.2874	$18.29	$18.30	$18.30
Purchase #3	$229.44	10.505%	$253.5427	$253.54	$253.55	$253.50
Purchase #4	$250.70	4.443%	$261.8386	$261.84	$261.85	$261.80
Purchase #5	$42.79	5.732%	$45.2427	$45.24	$45.25	$45.20
Purchase #6	$40.38	4.821%	$42.3267	$42.33	$42.35	$42.30
Purchase #7	$43.84	12.474%	$49.3086	$49.31	$49.30	$49.30
7 purchase totals =	$756.29		$811.3294	$811.33	$811.40	$811.20