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	$106.90	5.635%	$112.9238	$112.92	$112.90	$112.90
Purchase #2	$33.89	10.815%	$37.5552	$37.56	$37.55	$37.60
Purchase #3	$212.49	13.787%	$241.786	$241.79	$241.80	$241.80
Purchase #4	$182.36	12.354%	$204.8888	$204.89	$204.90	$204.90
Purchase #5	$103.64	3.549%	$107.3182	$107.32	$107.30	$107.30
Purchase #6	$55.53	12.697%	$62.5806	$62.58	$62.60	$62.60
Purchase #7	$32.79	13.666%	$37.2711	$37.27	$37.25	$37.30
7 purchase totals =	$727.60		$804.3237	$804.33	$804.30	$804.40