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	$159.52	7.849%	$172.0407	$172.04	$172.05	$172.00
Purchase #2	$142.29	9.159%	$155.3223	$155.32	$155.30	$155.30
Purchase #3	$140.99	6.802%	$150.5801	$150.58	$150.60	$150.60
Purchase #4	$200.38	6.802%	$214.0098	$214.01	$214.00	$214.00
Purchase #5	$53.29	4.216%	$55.5367	$55.54	$55.55	$55.50
Purchase #6	$180.59	7.748%	$194.5821	$194.58	$194.60	$194.60
Purchase #7	$175.48	7.714%	$189.0165	$189.02	$189.00	$189.00
7 purchase totals =	$1,052.54		$1,131.0882	$1,131.09	$1,131.10	$1,131.00