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	$81.35	13.742%	$92.5291	$92.53	$92.55	$92.50
Purchase #2	$58.99	4.318%	$61.5372	$61.54	$61.55	$61.50
Purchase #3	$22.40	10.789%	$24.8167	$24.82	$24.80	$24.80
Purchase #4	$179.48	6.470%	$191.0924	$191.09	$191.10	$191.10
Purchase #5	$150.88	3.588%	$156.2936	$156.29	$156.30	$156.30
Purchase #6	$205.62	9.260%	$224.6604	$224.66	$224.65	$224.70
Purchase #7	$238.56	6.728%	$254.6103	$254.61	$254.60	$254.60
7 purchase totals =	$937.28		$1,005.5397	$1,005.54	$1,005.55	$1,005.50