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	$91.67	11.160%	$101.9004	$101.90	$101.90	$101.90
Purchase #2	$40.67	11.423%	$45.3157	$45.32	$45.30	$45.30
Purchase #3	$125.62	6.736%	$134.0818	$134.08	$134.10	$134.10
Purchase #4	$185.41	10.256%	$204.4256	$204.43	$204.45	$204.40
Purchase #5	$58.27	9.110%	$63.5784	$63.58	$63.60	$63.60
Purchase #6	$54.37	10.212%	$59.9223	$59.92	$59.90	$59.90
Purchase #7	$170.29	12.399%	$191.4043	$191.40	$191.40	$191.40
7 purchase totals =	$726.30		$800.6285	$800.63	$800.65	$800.60