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	$232.77	6.548%	$248.0118	$248.01	$248.00	$248.00
Purchase #2	$97.60	5.286%	$102.7591	$102.76	$102.75	$102.80
Purchase #3	$150.70	11.221%	$167.61	$167.61	$167.60	$167.60
Purchase #4	$172.90	6.142%	$183.5195	$183.52	$183.50	$183.50
Purchase #5	$42.56	6.147%	$45.1762	$45.18	$45.20	$45.20
Purchase #6	$209.30	12.807%	$236.1051	$236.11	$236.10	$236.10
Purchase #7	$119.67	6.239%	$127.1362	$127.14	$127.15	$127.10
7 purchase totals =	$1,025.50		$1,110.3179	$1,110.33	$1,110.30	$1,110.30