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	$58.72	4.401%	$61.3043	$61.30	$61.30	$61.30
Purchase #2	$51.85	5.317%	$54.6069	$54.61	$54.60	$54.60
Purchase #3	$171.97	6.868%	$183.7809	$183.78	$183.80	$183.80
Purchase #4	$104.81	11.139%	$116.4848	$116.48	$116.50	$116.50
Purchase #5	$19.32	5.253%	$20.3349	$20.33	$20.35	$20.30
Purchase #6	$11.40	8.722%	$12.3943	$12.39	$12.40	$12.40
Purchase #7	$137.32	9.494%	$150.3572	$150.36	$150.35	$150.40
7 purchase totals =	$555.39		$599.2633	$599.25	$599.30	$599.30