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	$196.78	8.528%	$213.5614	$213.56	$213.55	$213.60
Purchase #2	$39.90	7.314%	$42.8183	$42.82	$42.80	$42.80
Purchase #3	$127.89	4.862%	$134.108	$134.11	$134.10	$134.10
Purchase #4	$26.54	4.332%	$27.6897	$27.69	$27.70	$27.70
Purchase #5	$243.48	5.612%	$257.1441	$257.14	$257.15	$257.10
Purchase #6	$130.63	5.753%	$138.1451	$138.15	$138.15	$138.10
Purchase #7	$115.85	6.473%	$123.349	$123.35	$123.35	$123.30
7 purchase totals =	$881.07		$936.8156	$936.82	$936.80	$936.70