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	$164.28	3.212%	$169.5567	$169.56	$169.55	$169.60
Purchase #2	$169.89	7.607%	$182.8135	$182.81	$182.80	$182.80
Purchase #3	$172.47	13.720%	$196.1329	$196.13	$196.15	$196.10
Purchase #4	$247.45	3.202%	$255.3733	$255.37	$255.35	$255.40
Purchase #5	$194.56	7.413%	$208.9827	$208.98	$209.00	$209.00
Purchase #6	$114.98	12.524%	$129.3801	$129.38	$129.40	$129.40
Purchase #7	$22.72	9.198%	$24.8098	$24.81	$24.80	$24.80
7 purchase totals =	$1,086.35		$1,167.0490	$1,167.04	$1,167.05	$1,167.10