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	$208.68	6.476%	$222.1941	$222.19	$222.20	$222.20
Purchase #2	$6.79	12.790%	$7.6584	$7.66	$7.65	$7.70
Purchase #3	$156.98	6.222%	$166.7473	$166.75	$166.75	$166.70
Purchase #4	$111.69	10.651%	$123.5861	$123.59	$123.60	$123.60
Purchase #5	$211.29	5.216%	$222.3109	$222.31	$222.30	$222.30
Purchase #6	$86.77	11.147%	$96.4423	$96.44	$96.45	$96.40
Purchase #7	$126.46	11.249%	$140.6855	$140.69	$140.70	$140.70
7 purchase totals =	$908.66		$979.6246	$979.63	$979.65	$979.60