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	$82.83	7.167%	$88.7664	$88.77	$88.75	$88.80
Purchase #2	$232.84	9.775%	$255.6001	$255.60	$255.60	$255.60
Purchase #3	$133.28	5.826%	$141.0449	$141.04	$141.05	$141.00
Purchase #4	$169.76	7.714%	$182.8553	$182.86	$182.85	$182.90
Purchase #5	$106.46	3.791%	$110.4959	$110.50	$110.50	$110.50
Purchase #6	$35.79	7.155%	$38.3508	$38.35	$38.35	$38.40
Purchase #7	$181.86	11.482%	$202.7412	$202.74	$202.75	$202.70
7 purchase totals =	$942.82		$1,019.8546	$1,019.86	$1,019.85	$1,019.90