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	$219.25	8.219%	$237.2702	$237.27	$237.25	$237.30
Purchase #2	$42.33	7.610%	$45.5513	$45.55	$45.55	$45.60
Purchase #3	$152.38	6.368%	$162.0836	$162.08	$162.10	$162.10
Purchase #4	$108.30	7.123%	$116.0142	$116.01	$116.00	$116.00
Purchase #5	$137.92	6.557%	$146.9634	$146.96	$146.95	$147.00
Purchase #6	$101.26	9.731%	$111.1136	$111.11	$111.10	$111.10
Purchase #7	$85.72	5.105%	$90.096	$90.10	$90.10	$90.10
7 purchase totals =	$847.16		$909.0923	$909.08	$909.05	$909.20