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	$32.91	5.276%	$34.6463	$34.65	$34.65	$34.60
Purchase #2	$168.61	6.489%	$179.5511	$179.55	$179.55	$179.60
Purchase #3	$236.75	11.440%	$263.8342	$263.83	$263.85	$263.80
Purchase #4	$156.61	11.702%	$174.9365	$174.94	$174.95	$174.90
Purchase #5	$67.30	13.327%	$76.2691	$76.27	$76.25	$76.30
Purchase #6	$32.76	11.585%	$36.5552	$36.56	$36.55	$36.60
Purchase #7	$77.88	5.809%	$82.404	$82.40	$82.40	$82.40
7 purchase totals =	$772.82		$848.1964	$848.20	$848.20	$848.20