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	$216.36	5.856%	$229.03	$229.03	$229.05	$229.00
Purchase #2	$34.86	6.524%	$37.1343	$37.13	$37.15	$37.10
Purchase #3	$190.28	4.751%	$199.3202	$199.32	$199.30	$199.30
Purchase #4	$234.30	11.447%	$261.1203	$261.12	$261.10	$261.10
Purchase #5	$142.88	10.790%	$158.2968	$158.30	$158.30	$158.30
Purchase #6	$51.78	5.778%	$54.7718	$54.77	$54.75	$54.80
Purchase #7	$146.46	8.183%	$158.4448	$158.44	$158.45	$158.40
7 purchase totals =	$1,016.92		$1,098.1182	$1,098.11	$1,098.10	$1,098.00