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	$67.40	6.469%	$71.7601	$71.76	$71.75	$71.80
Purchase #2	$78.67	4.320%	$82.0685	$82.07	$82.05	$82.10
Purchase #3	$48.55	7.353%	$52.1199	$52.12	$52.10	$52.10
Purchase #4	$209.99	7.845%	$226.4637	$226.46	$226.45	$226.50
Purchase #5	$108.75	10.276%	$119.9252	$119.93	$119.95	$119.90
Purchase #6	$214.48	11.139%	$238.3709	$238.37	$238.35	$238.40
Purchase #7	$92.64	9.496%	$101.4371	$101.44	$101.45	$101.40
7 purchase totals =	$820.48		$892.1454	$892.15	$892.10	$892.20