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	$178.78	11.663%	$199.6311	$199.63	$199.65	$199.60
Purchase #2	$66.46	7.641%	$71.5382	$71.54	$71.55	$71.50
Purchase #3	$68.80	4.391%	$71.821	$71.82	$71.80	$71.80
Purchase #4	$90.59	3.514%	$93.7733	$93.77	$93.75	$93.80
Purchase #5	$38.30	6.732%	$40.8784	$40.88	$40.90	$40.90
Purchase #6	$78.70	6.755%	$84.0162	$84.02	$84.00	$84.00
Purchase #7	$77.92	13.738%	$88.6246	$88.62	$88.60	$88.60
7 purchase totals =	$599.55		$650.2828	$650.28	$650.25	$650.20