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	$116.89	9.349%	$127.818	$127.82	$127.80	$127.80
Purchase #2	$156.34	3.111%	$161.2037	$161.20	$161.20	$161.20
Purchase #3	$102.39	8.814%	$111.4147	$111.41	$111.40	$111.40
Purchase #4	$30.56	4.380%	$31.8985	$31.90	$31.90	$31.90
Purchase #5	$115.70	5.162%	$121.6724	$121.67	$121.65	$121.70
Purchase #6	$51.99	9.498%	$56.928	$56.93	$56.95	$56.90
Purchase #7	$146.29	11.115%	$162.5501	$162.55	$162.55	$162.60
7 purchase totals =	$720.16		$773.4854	$773.48	$773.45	$773.50