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	$197.66	8.819%	$215.0916	$215.09	$215.10	$215.10
Purchase #2	$89.40	7.722%	$96.3035	$96.30	$96.30	$96.30
Purchase #3	$179.25	6.263%	$190.4764	$190.48	$190.50	$190.50
Purchase #4	$68.85	4.122%	$71.688	$71.69	$71.70	$71.70
Purchase #5	$218.61	4.266%	$227.9359	$227.94	$227.95	$227.90
Purchase #6	$35.56	9.163%	$38.8184	$38.82	$38.80	$38.80
Purchase #7	$209.30	11.788%	$233.9723	$233.97	$233.95	$234.00
7 purchase totals =	$998.63		$1,074.2861	$1,074.29	$1,074.30	$1,074.30