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	$40.87	10.242%	$45.0559	$45.06	$45.05	$45.10
Purchase #2	$64.39	11.641%	$71.8856	$71.89	$71.90	$71.90
Purchase #3	$22.31	12.797%	$25.165	$25.17	$25.15	$25.20
Purchase #4	$123.70	12.364%	$138.9943	$138.99	$139.00	$139.00
Purchase #5	$170.80	8.526%	$185.3624	$185.36	$185.35	$185.40
Purchase #6	$227.38	12.158%	$255.0249	$255.02	$255.00	$255.00
Purchase #7	$208.61	6.506%	$222.1822	$222.18	$222.20	$222.20
7 purchase totals =	$858.06		$943.6703	$943.67	$943.65	$943.80