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	$224.50	6.230%	$238.4864	$238.49	$238.50	$238.50
Purchase #2	$186.82	7.368%	$200.5849	$200.58	$200.60	$200.60
Purchase #3	$114.40	4.517%	$119.5674	$119.57	$119.55	$119.60
Purchase #4	$94.41	7.789%	$101.7636	$101.76	$101.75	$101.80
Purchase #5	$70.25	4.269%	$73.249	$73.25	$73.25	$73.20
Purchase #6	$170.61	6.421%	$181.5649	$181.56	$181.55	$181.60
Purchase #7	$217.56	10.336%	$240.047	$240.05	$240.05	$240.00
7 purchase totals =	$1,078.55		$1,155.2632	$1,155.26	$1,155.25	$1,155.30