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	$33.65	3.501%	$34.8281	$34.83	$34.85	$34.80
Purchase #2	$94.42	6.309%	$100.377	$100.38	$100.40	$100.40
Purchase #3	$186.89	13.162%	$211.4885	$211.49	$211.50	$211.50
Purchase #4	$173.84	3.241%	$179.4742	$179.47	$179.45	$179.50
Purchase #5	$149.96	9.404%	$164.0622	$164.06	$164.05	$164.10
Purchase #6	$194.46	7.779%	$209.587	$209.59	$209.60	$209.60
Purchase #7	$148.66	11.428%	$165.6489	$165.65	$165.65	$165.60
7 purchase totals =	$981.88		$1,065.4659	$1,065.47	$1,065.50	$1,065.50