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	$151.93	13.424%	$172.3251	$172.33	$172.35	$172.30
Purchase #2	$46.52	9.873%	$51.1129	$51.11	$51.10	$51.10
Purchase #3	$87.65	12.365%	$98.4879	$98.49	$98.50	$98.50
Purchase #4	$46.25	12.277%	$51.9281	$51.93	$51.95	$51.90
Purchase #5	$171.36	9.414%	$187.4918	$187.49	$187.50	$187.50
Purchase #6	$62.94	4.198%	$65.5822	$65.58	$65.60	$65.60
Purchase #7	$209.90	4.746%	$219.8619	$219.86	$219.85	$219.90
7 purchase totals =	$776.55		$846.7899	$846.79	$846.85	$846.80