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	$167.27	11.148%	$185.9173	$185.92	$185.90	$185.90
Purchase #2	$177.44	4.179%	$184.8552	$184.86	$184.85	$184.90
Purchase #3	$125.80	10.797%	$139.3826	$139.38	$139.40	$139.40
Purchase #4	$51.99	8.791%	$56.5604	$56.56	$56.55	$56.60
Purchase #5	$208.76	4.377%	$217.8974	$217.90	$217.90	$217.90
Purchase #6	$64.96	8.767%	$70.655	$70.66	$70.65	$70.70
Purchase #7	$38.38	6.405%	$40.8382	$40.84	$40.85	$40.80
7 purchase totals =	$834.60		$896.1061	$896.12	$896.10	$896.20