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	$220.44	10.794%	$244.2343	$244.23	$244.25	$244.20
Purchase #2	$210.61	3.511%	$218.0045	$218.00	$218.00	$218.00
Purchase #3	$148.78	9.458%	$162.8516	$162.85	$162.85	$162.90
Purchase #4	$89.36	11.588%	$99.715	$99.72	$99.70	$99.70
Purchase #5	$219.54	10.490%	$242.5697	$242.57	$242.55	$242.60
Purchase #6	$52.56	10.552%	$58.1061	$58.11	$58.10	$58.10
Purchase #7	$51.86	8.857%	$56.4532	$56.45	$56.45	$56.50
7 purchase totals =	$993.15		$1,081.9344	$1,081.93	$1,081.90	$1,082.00