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	$79.77	10.559%	$88.1929	$88.19	$88.20	$88.20
Purchase #2	$7.51	3.112%	$7.7437	$7.74	$7.75	$7.70
Purchase #3	$117.63	11.862%	$131.5833	$131.58	$131.60	$131.60
Purchase #4	$163.47	13.838%	$186.091	$186.09	$186.10	$186.10
Purchase #5	$147.88	5.127%	$155.4618	$155.46	$155.45	$155.50
Purchase #6	$92.52	4.439%	$96.627	$96.63	$96.65	$96.60
Purchase #7	$85.59	8.481%	$92.8489	$92.85	$92.85	$92.80
7 purchase totals =	$694.37		$758.5486	$758.54	$758.60	$758.50