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	$53.60	12.485%	$60.292	$60.29	$60.30	$60.30
Purchase #2	$246.87	5.424%	$260.2602	$260.26	$260.25	$260.30
Purchase #3	$82.36	13.805%	$93.7298	$93.73	$93.75	$93.70
Purchase #4	$141.82	10.650%	$156.9238	$156.92	$156.90	$156.90
Purchase #5	$233.89	9.256%	$255.5389	$255.54	$255.55	$255.50
Purchase #6	$86.66	10.756%	$95.9811	$95.98	$96.00	$96.00
Purchase #7	$213.26	4.233%	$222.2873	$222.29	$222.30	$222.30
7 purchase totals =	$1,058.46		$1,145.0131	$1,145.01	$1,145.05	$1,145.00