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	$185.30	7.503%	$199.2031	$199.20	$199.20	$199.20
Purchase #2	$69.52	11.676%	$77.6372	$77.64	$77.65	$77.60
Purchase #3	$41.62	4.366%	$43.4371	$43.44	$43.45	$43.40
Purchase #4	$48.75	13.535%	$55.3483	$55.35	$55.35	$55.30
Purchase #5	$176.94	8.292%	$191.6119	$191.61	$191.60	$191.60
Purchase #6	$200.43	12.673%	$225.8305	$225.83	$225.85	$225.80
Purchase #7	$195.32	7.216%	$209.4143	$209.41	$209.40	$209.40
7 purchase totals =	$917.88		$1,002.4824	$1,002.48	$1,002.50	$1,002.30