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	$93.52	3.658%	$96.941	$96.94	$96.95	$96.90
Purchase #2	$107.89	4.592%	$112.8443	$112.84	$112.85	$112.80
Purchase #3	$139.69	8.532%	$151.6084	$151.61	$151.60	$151.60
Purchase #4	$37.61	9.625%	$41.23	$41.23	$41.25	$41.20
Purchase #5	$173.62	12.272%	$194.9266	$194.93	$194.95	$194.90
Purchase #6	$241.35	7.327%	$259.0337	$259.03	$259.05	$259.00
Purchase #7	$81.36	5.376%	$85.7339	$85.73	$85.75	$85.70
7 purchase totals =	$875.04		$942.3179	$942.31	$942.40	$942.10