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	$194.48	4.538%	$203.3055	$203.31	$203.30	$203.30
Purchase #2	$188.42	4.255%	$196.4373	$196.44	$196.45	$196.40
Purchase #3	$130.74	9.846%	$143.6127	$143.61	$143.60	$143.60
Purchase #4	$219.71	10.225%	$242.1753	$242.18	$242.20	$242.20
Purchase #5	$100.42	7.482%	$107.9334	$107.93	$107.95	$107.90
Purchase #6	$90.97	3.670%	$94.3086	$94.31	$94.30	$94.30
Purchase #7	$40.65	3.453%	$42.0536	$42.05	$42.05	$42.10
7 purchase totals =	$965.39		$1,029.8264	$1,029.83	$1,029.85	$1,029.80