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	$175.99	10.679%	$194.784	$194.78	$194.80	$194.80
Purchase #2	$142.38	5.717%	$150.5199	$150.52	$150.50	$150.50
Purchase #3	$30.28	8.467%	$32.8438	$32.84	$32.85	$32.80
Purchase #4	$240.64	4.741%	$252.0487	$252.05	$252.05	$252.00
Purchase #5	$145.75	3.404%	$150.7113	$150.71	$150.70	$150.70
Purchase #6	$236.87	7.662%	$255.019	$255.02	$255.00	$255.00
Purchase #7	$40.41	7.757%	$43.5446	$43.54	$43.55	$43.50
7 purchase totals =	$1,012.32		$1,079.4713	$1,079.46	$1,079.45	$1,079.30