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	$220.88	6.473%	$235.1776	$235.18	$235.20	$235.20
Purchase #2	$146.99	3.124%	$151.582	$151.58	$151.60	$151.60
Purchase #3	$80.78	11.212%	$89.8371	$89.84	$89.85	$89.80
Purchase #4	$125.50	12.457%	$141.1335	$141.13	$141.15	$141.10
Purchase #5	$156.57	5.208%	$164.7242	$164.72	$164.70	$164.70
Purchase #6	$75.96	5.722%	$80.3064	$80.31	$80.30	$80.30
Purchase #7	$179.42	11.358%	$199.7985	$199.80	$199.80	$199.80
7 purchase totals =	$986.10		$1,062.5593	$1,062.56	$1,062.60	$1,062.50