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	$182.76	6.825%	$195.2334	$195.23	$195.25	$195.20
Purchase #2	$56.48	10.503%	$62.4121	$62.41	$62.40	$62.40
Purchase #3	$231.34	11.114%	$257.0511	$257.05	$257.05	$257.10
Purchase #4	$101.95	13.408%	$115.6195	$115.62	$115.60	$115.60
Purchase #5	$27.80	12.843%	$31.3704	$31.37	$31.35	$31.40
Purchase #6	$47.94	5.383%	$50.5206	$50.52	$50.50	$50.50
Purchase #7	$85.47	4.744%	$89.5247	$89.52	$89.50	$89.50
7 purchase totals =	$733.74		$801.7318	$801.72	$801.65	$801.70