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	$27.90	8.291%	$30.2132	$30.21	$30.20	$30.20
Purchase #2	$148.80	8.538%	$161.5045	$161.50	$161.50	$161.50
Purchase #3	$168.34	6.162%	$178.7131	$178.71	$178.70	$178.70
Purchase #4	$87.39	13.739%	$99.3965	$99.40	$99.40	$99.40
Purchase #5	$196.68	10.274%	$216.8869	$216.89	$216.90	$216.90
Purchase #6	$245.75	4.751%	$257.4256	$257.43	$257.45	$257.40
Purchase #7	$55.32	8.334%	$59.9304	$59.93	$59.95	$59.90
7 purchase totals =	$930.18		$1,004.0702	$1,004.07	$1,004.10	$1,004.00