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	$142.95	5.230%	$150.4263	$150.43	$150.45	$150.40
Purchase #2	$17.48	8.133%	$18.9016	$18.90	$18.90	$18.90
Purchase #3	$103.31	5.839%	$109.3423	$109.34	$109.35	$109.30
Purchase #4	$185.41	7.751%	$199.7811	$199.78	$199.80	$199.80
Purchase #5	$182.41	3.474%	$188.7469	$188.75	$188.75	$188.70
Purchase #6	$209.97	10.755%	$232.5523	$232.55	$232.55	$232.60
Purchase #7	$68.84	13.348%	$78.0288	$78.03	$78.05	$78.00
7 purchase totals =	$910.37		$977.7793	$977.78	$977.85	$977.70