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	$169.28	10.456%	$186.9799	$186.98	$187.00	$187.00
Purchase #2	$91.83	4.624%	$96.0762	$96.08	$96.10	$96.10
Purchase #3	$73.45	8.673%	$79.8203	$79.82	$79.80	$79.80
Purchase #4	$93.72	12.807%	$105.7227	$105.72	$105.70	$105.70
Purchase #5	$219.53	5.304%	$231.1739	$231.17	$231.15	$231.20
Purchase #6	$210.86	5.398%	$222.2422	$222.24	$222.25	$222.20
Purchase #7	$78.64	8.736%	$85.51	$85.51	$85.50	$85.50
7 purchase totals =	$937.31		$1,007.5252	$1,007.52	$1,007.50	$1,007.50