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	$64.58	11.630%	$72.0907	$72.09	$72.10	$72.10
Purchase #2	$6.69	10.608%	$7.3997	$7.40	$7.40	$7.40
Purchase #3	$191.28	7.419%	$205.4711	$205.47	$205.45	$205.50
Purchase #4	$246.80	7.839%	$266.1467	$266.15	$266.15	$266.10
Purchase #5	$141.79	10.650%	$156.8906	$156.89	$156.90	$156.90
Purchase #6	$93.78	11.116%	$104.2046	$104.20	$104.20	$104.20
Purchase #7	$221.74	12.373%	$249.1759	$249.18	$249.20	$249.20
7 purchase totals =	$966.66		$1,061.3793	$1,061.38	$1,061.40	$1,061.40