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	$209.44	3.466%	$216.6992	$216.70	$216.70	$216.70
Purchase #2	$69.79	10.236%	$76.9337	$76.93	$76.95	$76.90
Purchase #3	$54.93	7.852%	$59.2431	$59.24	$59.25	$59.20
Purchase #4	$241.77	5.115%	$254.1365	$254.14	$254.15	$254.10
Purchase #5	$66.33	6.361%	$70.5493	$70.55	$70.55	$70.50
Purchase #6	$63.96	10.201%	$70.4846	$70.48	$70.50	$70.50
Purchase #7	$185.49	4.814%	$194.4195	$194.42	$194.40	$194.40
7 purchase totals =	$891.71		$942.4659	$942.46	$942.50	$942.30