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	$192.25	4.291%	$200.4994	$200.50	$200.50	$200.50
Purchase #2	$169.88	9.232%	$185.5633	$185.56	$185.55	$185.60
Purchase #3	$45.52	5.829%	$48.1734	$48.17	$48.15	$48.20
Purchase #4	$228.61	13.700%	$259.9296	$259.93	$259.95	$259.90
Purchase #5	$225.64	11.477%	$251.5367	$251.54	$251.55	$251.50
Purchase #6	$73.27	7.178%	$78.5293	$78.53	$78.55	$78.50
Purchase #7	$215.69	11.297%	$240.0565	$240.06	$240.05	$240.10
7 purchase totals =	$1,150.86		$1,264.2882	$1,264.29	$1,264.30	$1,264.30