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	$30.42	9.425%	$33.2871	$33.29	$33.30	$33.30
Purchase #2	$142.66	4.182%	$148.626	$148.63	$148.65	$148.60
Purchase #3	$163.41	10.450%	$180.4863	$180.49	$180.50	$180.50
Purchase #4	$91.85	8.614%	$99.762	$99.76	$99.75	$99.80
Purchase #5	$74.76	6.834%	$79.8691	$79.87	$79.85	$79.90
Purchase #6	$182.83	12.387%	$205.4772	$205.48	$205.50	$205.50
Purchase #7	$246.41	6.513%	$262.4587	$262.46	$262.45	$262.50
7 purchase totals =	$932.34		$1,009.9664	$1,009.98	$1,010.00	$1,010.10