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	$201.33	7.483%	$216.3955	$216.40	$216.40	$216.40
Purchase #2	$99.82	10.116%	$109.9178	$109.92	$109.90	$109.90
Purchase #3	$168.96	6.717%	$180.309	$180.31	$180.30	$180.30
Purchase #4	$76.27	13.128%	$86.2827	$86.28	$86.30	$86.30
Purchase #5	$99.84	4.665%	$104.4975	$104.50	$104.50	$104.50
Purchase #6	$231.34	11.156%	$257.1483	$257.15	$257.15	$257.10
Purchase #7	$107.67	5.596%	$113.6952	$113.70	$113.70	$113.70
7 purchase totals =	$985.23		$1,068.2460	$1,068.26	$1,068.25	$1,068.20