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	$219.91	9.755%	$241.3622	$241.36	$241.35	$241.40
Purchase #2	$80.39	11.333%	$89.5006	$89.50	$89.50	$89.50
Purchase #3	$33.85	9.651%	$37.1169	$37.12	$37.10	$37.10
Purchase #4	$107.54	8.694%	$116.8895	$116.89	$116.90	$116.90
Purchase #5	$125.25	4.684%	$131.1167	$131.12	$131.10	$131.10
Purchase #6	$170.81	4.588%	$178.6468	$178.65	$178.65	$178.60
Purchase #7	$242.47	11.261%	$269.7745	$269.77	$269.75	$269.80
7 purchase totals =	$980.22		$1,064.4072	$1,064.41	$1,064.35	$1,064.40