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	$89.73	8.544%	$97.3965	$97.40	$97.40	$97.40
Purchase #2	$79.50	13.840%	$90.5028	$90.50	$90.50	$90.50
Purchase #3	$110.49	11.770%	$123.4947	$123.49	$123.50	$123.50
Purchase #4	$127.67	10.483%	$141.0536	$141.05	$141.05	$141.10
Purchase #5	$208.98	7.226%	$224.0809	$224.08	$224.10	$224.10
Purchase #6	$183.94	4.128%	$191.533	$191.53	$191.55	$191.50
Purchase #7	$210.55	5.722%	$222.5977	$222.60	$222.60	$222.60
7 purchase totals =	$1,010.86		$1,090.6592	$1,090.65	$1,090.70	$1,090.70