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	$76.79	11.707%	$85.7798	$85.78	$85.80	$85.80
Purchase #2	$105.29	3.848%	$109.3416	$109.34	$109.35	$109.30
Purchase #3	$195.70	11.645%	$218.4893	$218.49	$218.50	$218.50
Purchase #4	$171.49	6.469%	$182.5837	$182.58	$182.60	$182.60
Purchase #5	$227.93	11.460%	$254.0508	$254.05	$254.05	$254.10
Purchase #6	$171.51	11.727%	$191.623	$191.62	$191.60	$191.60
Purchase #7	$77.25	11.690%	$86.2805	$86.28	$86.30	$86.30
7 purchase totals =	$1,025.96		$1,128.1487	$1,128.14	$1,128.20	$1,128.20