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	$136.31	11.528%	$152.0238	$152.02	$152.00	$152.00
Purchase #2	$185.89	6.435%	$197.852	$197.85	$197.85	$197.90
Purchase #3	$218.33	11.323%	$243.0515	$243.05	$243.05	$243.10
Purchase #4	$225.42	5.569%	$237.9736	$237.97	$237.95	$238.00
Purchase #5	$116.43	10.384%	$128.5201	$128.52	$128.50	$128.50
Purchase #6	$18.77	3.821%	$19.4872	$19.49	$19.50	$19.50
Purchase #7	$77.88	5.483%	$82.1502	$82.15	$82.15	$82.20
7 purchase totals =	$979.03		$1,061.0584	$1,061.05	$1,061.00	$1,061.20