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	$37.40	6.550%	$39.8497	$39.85	$39.85	$39.80
Purchase #2	$90.73	9.752%	$99.578	$99.58	$99.60	$99.60
Purchase #3	$126.39	8.640%	$137.3101	$137.31	$137.30	$137.30
Purchase #4	$23.71	8.653%	$25.7616	$25.76	$25.75	$25.80
Purchase #5	$128.92	3.596%	$133.556	$133.56	$133.55	$133.60
Purchase #6	$200.39	4.205%	$208.8164	$208.82	$208.80	$208.80
Purchase #7	$98.36	5.115%	$103.3911	$103.39	$103.40	$103.40
7 purchase totals =	$705.90		$748.2629	$748.27	$748.25	$748.30