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	$120.63	5.794%	$127.6193	$127.62	$127.60	$127.60
Purchase #2	$31.52	5.829%	$33.3573	$33.36	$33.35	$33.40
Purchase #3	$81.25	8.215%	$87.9247	$87.92	$87.90	$87.90
Purchase #4	$47.43	4.221%	$49.432	$49.43	$49.45	$49.40
Purchase #5	$232.77	5.476%	$245.5165	$245.52	$245.50	$245.50
Purchase #6	$37.27	7.435%	$40.041	$40.04	$40.05	$40.00
Purchase #7	$189.98	11.581%	$211.9816	$211.98	$212.00	$212.00
7 purchase totals =	$740.85		$795.8724	$795.87	$795.85	$795.80