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	$78.46	11.582%	$87.5472	$87.55	$87.55	$87.50
Purchase #2	$78.65	10.108%	$86.5999	$86.60	$86.60	$86.60
Purchase #3	$202.28	10.262%	$223.038	$223.04	$223.05	$223.00
Purchase #4	$28.28	3.291%	$29.2107	$29.21	$29.20	$29.20
Purchase #5	$168.77	10.296%	$186.1466	$186.15	$186.15	$186.10
Purchase #6	$141.40	11.851%	$158.1573	$158.16	$158.15	$158.20
Purchase #7	$155.37	10.313%	$171.3933	$171.39	$171.40	$171.40
7 purchase totals =	$853.21		$942.0930	$942.10	$942.10	$942.00