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	$32.88	12.702%	$37.0564	$37.06	$37.05	$37.10
Purchase #2	$23.71	5.740%	$25.071	$25.07	$25.05	$25.10
Purchase #3	$9.82	5.736%	$10.3833	$10.38	$10.40	$10.40
Purchase #4	$126.38	6.120%	$134.1145	$134.11	$134.10	$134.10
Purchase #5	$137.87	4.868%	$144.5815	$144.58	$144.60	$144.60
Purchase #6	$80.86	12.283%	$90.792	$90.79	$90.80	$90.80
Purchase #7	$250.55	5.128%	$263.3982	$263.40	$263.40	$263.40
7 purchase totals =	$662.07		$705.3969	$705.39	$705.40	$705.50