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	$145.63	9.459%	$159.4051	$159.41	$159.40	$159.40
Purchase #2	$94.93	11.454%	$105.8033	$105.80	$105.80	$105.80
Purchase #3	$48.85	4.420%	$51.0092	$51.01	$51.00	$51.00
Purchase #4	$19.53	12.378%	$21.9474	$21.95	$21.95	$21.90
Purchase #5	$61.86	8.849%	$67.334	$67.33	$67.35	$67.30
Purchase #6	$152.32	5.236%	$160.2955	$160.30	$160.30	$160.30
Purchase #7	$176.30	8.655%	$191.5588	$191.56	$191.55	$191.60
7 purchase totals =	$699.42		$757.3533	$757.36	$757.35	$757.30