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	$71.41	9.330%	$78.0726	$78.07	$78.05	$78.10
Purchase #2	$190.55	7.334%	$204.5249	$204.52	$204.50	$204.50
Purchase #3	$168.42	3.120%	$173.6747	$173.67	$173.65	$173.70
Purchase #4	$104.32	4.674%	$109.1959	$109.20	$109.20	$109.20
Purchase #5	$212.74	11.334%	$236.852	$236.85	$236.85	$236.90
Purchase #6	$162.80	6.528%	$173.4276	$173.43	$173.45	$173.40
Purchase #7	$136.96	4.166%	$142.6658	$142.67	$142.65	$142.70
7 purchase totals =	$1,047.20		$1,118.4135	$1,118.41	$1,118.35	$1,118.50