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	$73.64	3.498%	$76.2159	$76.22	$76.20	$76.20
Purchase #2	$61.59	11.857%	$68.8927	$68.89	$68.90	$68.90
Purchase #3	$76.54	6.157%	$81.2526	$81.25	$81.25	$81.30
Purchase #4	$145.58	7.521%	$156.5291	$156.53	$156.55	$156.50
Purchase #5	$105.71	5.862%	$111.9067	$111.91	$111.90	$111.90
Purchase #6	$70.29	9.136%	$76.7117	$76.71	$76.70	$76.70
Purchase #7	$198.72	7.644%	$213.9102	$213.91	$213.90	$213.90
7 purchase totals =	$732.07		$785.4189	$785.42	$785.40	$785.40