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	$55.92	9.275%	$61.1066	$61.11	$61.10	$61.10
Purchase #2	$191.60	11.540%	$213.7106	$213.71	$213.70	$213.70
Purchase #3	$150.55	5.603%	$158.9853	$158.99	$159.00	$159.00
Purchase #4	$176.46	6.674%	$188.2369	$188.24	$188.25	$188.20
Purchase #5	$139.97	8.273%	$151.5497	$151.55	$151.55	$151.50
Purchase #6	$38.43	12.190%	$43.1146	$43.11	$43.10	$43.10
Purchase #7	$79.85	3.486%	$82.6336	$82.63	$82.65	$82.60
7 purchase totals =	$832.78		$899.3373	$899.34	$899.35	$899.20