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	$215.40	11.497%	$240.1645	$240.16	$240.15	$240.20
Purchase #2	$130.62	5.448%	$137.7362	$137.74	$137.75	$137.70
Purchase #3	$101.49	3.869%	$105.4166	$105.42	$105.40	$105.40
Purchase #4	$74.97	4.498%	$78.3422	$78.34	$78.35	$78.30
Purchase #5	$212.72	9.760%	$233.4815	$233.48	$233.50	$233.50
Purchase #6	$191.37	5.140%	$201.2064	$201.21	$201.20	$201.20
Purchase #7	$104.93	6.160%	$111.3937	$111.39	$111.40	$111.40
7 purchase totals =	$1,031.50		$1,107.7411	$1,107.74	$1,107.75	$1,107.70