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	$62.43	7.690%	$67.2309	$67.23	$67.25	$67.20
Purchase #2	$238.77	6.170%	$253.5021	$253.50	$253.50	$253.50
Purchase #3	$189.26	6.577%	$201.7076	$201.71	$201.70	$201.70
Purchase #4	$79.33	12.395%	$89.163	$89.16	$89.15	$89.20
Purchase #5	$31.34	7.788%	$33.7808	$33.78	$33.80	$33.80
Purchase #6	$143.79	4.769%	$150.6473	$150.65	$150.65	$150.60
Purchase #7	$241.86	5.869%	$256.0548	$256.05	$256.05	$256.10
7 purchase totals =	$986.78		$1,052.0865	$1,052.08	$1,052.10	$1,052.10