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	$136.98	10.643%	$151.5588	$151.56	$151.55	$151.60
Purchase #2	$146.37	10.623%	$161.9189	$161.92	$161.90	$161.90
Purchase #3	$9.67	3.298%	$9.9889	$9.99	$10.00	$10.00
Purchase #4	$223.27	7.560%	$240.1492	$240.15	$240.15	$240.10
Purchase #5	$135.78	11.337%	$151.1734	$151.17	$151.15	$151.20
Purchase #6	$144.43	6.310%	$153.5435	$153.54	$153.55	$153.50
Purchase #7	$126.46	6.705%	$134.9391	$134.94	$134.95	$134.90
7 purchase totals =	$922.96		$1,003.2718	$1,003.27	$1,003.25	$1,003.20