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	$56.57	11.174%	$62.8911	$62.89	$62.90	$62.90
Purchase #2	$245.35	8.776%	$266.8819	$266.88	$266.90	$266.90
Purchase #3	$199.75	4.483%	$208.7048	$208.70	$208.70	$208.70
Purchase #4	$73.86	6.372%	$78.5664	$78.57	$78.55	$78.60
Purchase #5	$137.82	3.117%	$142.1158	$142.12	$142.10	$142.10
Purchase #6	$219.69	11.575%	$245.1191	$245.12	$245.10	$245.10
Purchase #7	$60.79	6.700%	$64.8629	$64.86	$64.85	$64.90
7 purchase totals =	$993.83		$1,069.1420	$1,069.14	$1,069.10	$1,069.20