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	$78.33	10.738%	$86.7411	$86.74	$86.75	$86.70
Purchase #2	$122.98	10.502%	$135.8954	$135.90	$135.90	$135.90
Purchase #3	$54.94	8.377%	$59.5423	$59.54	$59.55	$59.50
Purchase #4	$154.44	5.279%	$162.5929	$162.59	$162.60	$162.60
Purchase #5	$200.32	11.173%	$222.7018	$222.70	$222.70	$222.70
Purchase #6	$117.51	4.556%	$122.8638	$122.86	$122.85	$122.90
Purchase #7	$55.98	3.200%	$57.7714	$57.77	$57.75	$57.80
7 purchase totals =	$784.50		$848.1087	$848.10	$848.10	$848.10