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	$70.87	10.557%	$78.3517	$78.35	$78.35	$78.40
Purchase #2	$127.32	3.459%	$131.724	$131.72	$131.70	$131.70
Purchase #3	$161.61	9.437%	$176.8611	$176.86	$176.85	$176.90
Purchase #4	$233.83	8.588%	$253.9113	$253.91	$253.90	$253.90
Purchase #5	$249.40	10.154%	$274.7241	$274.72	$274.70	$274.70
Purchase #6	$60.98	12.718%	$68.7354	$68.74	$68.75	$68.70
Purchase #7	$37.91	3.430%	$39.2103	$39.21	$39.20	$39.20
7 purchase totals =	$941.92		$1,023.5179	$1,023.51	$1,023.45	$1,023.50