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	$125.34	3.699%	$129.9763	$129.98	$130.00	$130.00
Purchase #2	$215.38	8.425%	$233.5258	$233.53	$233.55	$233.50
Purchase #3	$198.70	8.488%	$215.5657	$215.57	$215.55	$215.60
Purchase #4	$96.49	13.362%	$109.383	$109.38	$109.40	$109.40
Purchase #5	$78.60	10.192%	$86.6109	$86.61	$86.60	$86.60
Purchase #6	$37.27	10.677%	$41.2493	$41.25	$41.25	$41.20
Purchase #7	$116.93	13.262%	$132.4373	$132.44	$132.45	$132.40
7 purchase totals =	$868.71		$948.7483	$948.76	$948.80	$948.70