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	$78.47	10.312%	$86.5618	$86.56	$86.55	$86.60
Purchase #2	$229.67	11.244%	$255.4941	$255.49	$255.50	$255.50
Purchase #3	$238.44	11.132%	$264.9831	$264.98	$265.00	$265.00
Purchase #4	$37.32	8.573%	$40.5194	$40.52	$40.50	$40.50
Purchase #5	$212.38	13.211%	$240.4375	$240.44	$240.45	$240.40
Purchase #6	$201.31	13.764%	$229.0183	$229.02	$229.00	$229.00
Purchase #7	$34.52	11.473%	$38.4805	$38.48	$38.50	$38.50
7 purchase totals =	$1,032.11		$1,155.4947	$1,155.49	$1,155.50	$1,155.50