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	$96.33	4.677%	$100.8354	$100.84	$100.85	$100.80
Purchase #2	$156.77	7.805%	$169.0059	$169.01	$169.00	$169.00
Purchase #3	$111.33	6.746%	$118.8403	$118.84	$118.85	$118.80
Purchase #4	$229.64	11.764%	$256.6548	$256.65	$256.65	$256.70
Purchase #5	$154.96	7.624%	$166.7742	$166.77	$166.75	$166.80
Purchase #6	$192.33	6.665%	$205.1488	$205.15	$205.15	$205.10
Purchase #7	$104.46	8.801%	$113.6535	$113.65	$113.65	$113.70
7 purchase totals =	$1,045.82		$1,130.9129	$1,130.91	$1,130.90	$1,130.90