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	$106.88	4.860%	$112.0744	$112.07	$112.05	$112.10
Purchase #2	$131.83	9.691%	$144.6056	$144.61	$144.60	$144.60
Purchase #3	$142.26	10.258%	$156.853	$156.85	$156.85	$156.90
Purchase #4	$80.26	11.751%	$89.6914	$89.69	$89.70	$89.70
Purchase #5	$109.57	7.268%	$117.5335	$117.53	$117.55	$117.50
Purchase #6	$42.47	12.315%	$47.7002	$47.70	$47.70	$47.70
Purchase #7	$211.58	6.107%	$224.5012	$224.50	$224.50	$224.50
7 purchase totals =	$824.85		$892.9593	$892.95	$892.95	$893.00