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	$183.84	6.708%	$196.172	$196.17	$196.15	$196.20
Purchase #2	$105.69	6.301%	$112.3495	$112.35	$112.35	$112.30
Purchase #3	$53.42	8.498%	$57.9596	$57.96	$57.95	$58.00
Purchase #4	$155.29	3.336%	$160.4705	$160.47	$160.45	$160.50
Purchase #5	$44.86	4.232%	$46.7585	$46.76	$46.75	$46.80
Purchase #6	$59.43	3.666%	$61.6087	$61.61	$61.60	$61.60
Purchase #7	$73.47	6.367%	$78.1478	$78.15	$78.15	$78.10
7 purchase totals =	$676.00		$713.4666	$713.47	$713.40	$713.50