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	$125.74	9.730%	$137.9745	$137.97	$137.95	$138.00
Purchase #2	$239.58	5.828%	$253.5427	$253.54	$253.55	$253.50
Purchase #3	$93.28	11.179%	$103.7078	$103.71	$103.70	$103.70
Purchase #4	$157.80	4.152%	$164.3519	$164.35	$164.35	$164.40
Purchase #5	$103.92	5.214%	$109.3384	$109.34	$109.35	$109.30
Purchase #6	$59.90	8.414%	$64.94	$64.94	$64.95	$64.90
Purchase #7	$210.99	8.113%	$228.1076	$228.11	$228.10	$228.10
7 purchase totals =	$991.21		$1,061.9629	$1,061.96	$1,061.95	$1,061.90