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	$199.90	6.292%	$212.4777	$212.48	$212.50	$212.50
Purchase #2	$101.82	3.467%	$105.3501	$105.35	$105.35	$105.40
Purchase #3	$134.56	11.853%	$150.5094	$150.51	$150.50	$150.50
Purchase #4	$46.35	7.391%	$49.7757	$49.78	$49.80	$49.80
Purchase #5	$218.76	3.433%	$226.27	$226.27	$226.25	$226.30
Purchase #6	$81.29	13.473%	$92.2422	$92.24	$92.25	$92.20
Purchase #7	$34.52	8.787%	$37.5533	$37.55	$37.55	$37.60
7 purchase totals =	$817.20		$874.1784	$874.18	$874.20	$874.30