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	$133.59	4.844%	$140.0611	$140.06	$140.05	$140.10
Purchase #2	$123.42	5.422%	$130.1118	$130.11	$130.10	$130.10
Purchase #3	$46.66	12.466%	$52.4766	$52.48	$52.50	$52.50
Purchase #4	$90.34	3.523%	$93.5227	$93.52	$93.50	$93.50
Purchase #5	$158.90	3.864%	$165.0399	$165.04	$165.05	$165.00
Purchase #6	$24.88	12.417%	$27.9693	$27.97	$27.95	$28.00
Purchase #7	$50.78	6.345%	$54.002	$54.00	$54.00	$54.00
7 purchase totals =	$628.57		$663.1834	$663.18	$663.15	$663.20