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	$193.70	12.551%	$218.0113	$218.01	$218.00	$218.00
Purchase #2	$65.39	3.140%	$67.4432	$67.44	$67.45	$67.40
Purchase #3	$22.26	9.415%	$24.3558	$24.36	$24.35	$24.40
Purchase #4	$215.52	10.332%	$237.7875	$237.79	$237.80	$237.80
Purchase #5	$99.49	4.550%	$104.0168	$104.02	$104.00	$104.00
Purchase #6	$101.72	9.390%	$111.2715	$111.27	$111.25	$111.30
Purchase #7	$100.50	11.159%	$111.7148	$111.71	$111.70	$111.70
7 purchase totals =	$798.58		$874.6009	$874.60	$874.55	$874.60