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	$108.83	3.793%	$112.9579	$112.96	$112.95	$113.00
Purchase #2	$156.55	12.134%	$175.5458	$175.55	$175.55	$175.50
Purchase #3	$217.33	8.590%	$235.9986	$236.00	$236.00	$236.00
Purchase #4	$139.35	12.615%	$156.929	$156.93	$156.95	$156.90
Purchase #5	$79.41	13.253%	$89.9342	$89.93	$89.95	$89.90
Purchase #6	$40.92	6.543%	$43.5974	$43.60	$43.60	$43.60
Purchase #7	$85.50	12.568%	$96.2456	$96.25	$96.25	$96.20
7 purchase totals =	$827.89		$911.2085	$911.22	$911.25	$911.10