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	$179.39	8.290%	$194.2614	$194.26	$194.25	$194.30
Purchase #2	$136.40	12.804%	$153.8647	$153.86	$153.85	$153.90
Purchase #3	$188.55	11.210%	$209.6865	$209.69	$209.70	$209.70
Purchase #4	$99.52	5.314%	$104.8085	$104.81	$104.80	$104.80
Purchase #5	$99.63	11.575%	$111.1622	$111.16	$111.15	$111.20
Purchase #6	$52.60	8.408%	$57.0226	$57.02	$57.00	$57.00
Purchase #7	$231.79	7.588%	$249.3782	$249.38	$249.40	$249.40
7 purchase totals =	$987.88		$1,080.1841	$1,080.18	$1,080.15	$1,080.30