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	$139.55	7.756%	$150.3735	$150.37	$150.35	$150.40
Purchase #2	$94.69	6.482%	$100.8278	$100.83	$100.85	$100.80
Purchase #3	$145.87	11.835%	$163.1337	$163.13	$163.15	$163.10
Purchase #4	$81.62	10.686%	$90.3419	$90.34	$90.35	$90.30
Purchase #5	$65.43	8.369%	$70.9058	$70.91	$70.90	$70.90
Purchase #6	$184.72	8.634%	$200.6687	$200.67	$200.65	$200.70
Purchase #7	$217.46	5.268%	$228.9158	$228.92	$228.90	$228.90
7 purchase totals =	$929.34		$1,005.1672	$1,005.17	$1,005.15	$1,005.10