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	$197.27	13.116%	$223.1439	$223.14	$223.15	$223.10
Purchase #2	$162.94	4.103%	$169.6254	$169.63	$169.65	$169.60
Purchase #3	$191.60	13.865%	$218.1653	$218.17	$218.15	$218.20
Purchase #4	$201.88	12.240%	$226.5901	$226.59	$226.60	$226.60
Purchase #5	$10.36	4.823%	$10.8597	$10.86	$10.85	$10.90
Purchase #6	$112.72	4.123%	$117.3674	$117.37	$117.35	$117.40
Purchase #7	$48.83	6.260%	$51.8868	$51.89	$51.90	$51.90
7 purchase totals =	$925.60		$1,017.6386	$1,017.65	$1,017.65	$1,017.70