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	$82.45	4.160%	$85.8799	$85.88	$85.90	$85.90
Purchase #2	$127.92	8.478%	$138.7651	$138.77	$138.75	$138.80
Purchase #3	$193.72	4.454%	$202.3483	$202.35	$202.35	$202.30
Purchase #4	$174.95	7.522%	$188.1097	$188.11	$188.10	$188.10
Purchase #5	$77.27	7.222%	$82.8504	$82.85	$82.85	$82.90
Purchase #6	$65.38	7.578%	$70.3345	$70.33	$70.35	$70.30
Purchase #7	$111.61	4.730%	$116.8892	$116.89	$116.90	$116.90
7 purchase totals =	$833.30		$885.1771	$885.18	$885.20	$885.20