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	$185.82	13.720%	$211.3145	$211.31	$211.30	$211.30
Purchase #2	$33.25	12.445%	$37.388	$37.39	$37.40	$37.40
Purchase #3	$52.47	8.456%	$56.9069	$56.91	$56.90	$56.90
Purchase #4	$90.46	6.408%	$96.2567	$96.26	$96.25	$96.30
Purchase #5	$48.70	13.748%	$55.3953	$55.40	$55.40	$55.40
Purchase #6	$164.61	11.418%	$183.4052	$183.41	$183.40	$183.40
Purchase #7	$41.60	7.670%	$44.7907	$44.79	$44.80	$44.80
7 purchase totals =	$616.91		$685.4573	$685.47	$685.45	$685.50