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	$234.65	3.507%	$242.8792	$242.88	$242.90	$242.90
Purchase #2	$18.27	13.610%	$20.7565	$20.76	$20.75	$20.80
Purchase #3	$63.89	9.857%	$70.1876	$70.19	$70.20	$70.20
Purchase #4	$47.56	6.745%	$50.7679	$50.77	$50.75	$50.80
Purchase #5	$179.42	8.434%	$194.5523	$194.55	$194.55	$194.60
Purchase #6	$193.82	12.712%	$218.4584	$218.46	$218.45	$218.50
Purchase #7	$246.33	7.177%	$264.0091	$264.01	$264.00	$264.00
7 purchase totals =	$983.94		$1,061.6110	$1,061.62	$1,061.60	$1,061.80