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	$166.69	5.445%	$175.7663	$175.77	$175.75	$175.80
Purchase #2	$160.93	8.448%	$174.5254	$174.53	$174.55	$174.50
Purchase #3	$37.73	10.233%	$41.5909	$41.59	$41.60	$41.60
Purchase #4	$168.41	10.249%	$185.6703	$185.67	$185.65	$185.70
Purchase #5	$190.82	12.707%	$215.0675	$215.07	$215.05	$215.10
Purchase #6	$235.66	12.465%	$265.035	$265.04	$265.05	$265.00
Purchase #7	$119.39	3.713%	$123.823	$123.82	$123.80	$123.80
7 purchase totals =	$1,079.63		$1,181.4784	$1,181.49	$1,181.45	$1,181.50