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	$128.46	11.212%	$142.8629	$142.86	$142.85	$142.90
Purchase #2	$38.69	12.494%	$43.5239	$43.52	$43.50	$43.50
Purchase #3	$193.48	8.749%	$210.4076	$210.41	$210.40	$210.40
Purchase #4	$85.93	12.722%	$96.862	$96.86	$96.85	$96.90
Purchase #5	$181.60	13.640%	$206.3702	$206.37	$206.35	$206.40
Purchase #6	$96.59	5.390%	$101.7962	$101.80	$101.80	$101.80
Purchase #7	$221.46	11.699%	$247.3686	$247.37	$247.35	$247.40
7 purchase totals =	$946.21		$1,049.1914	$1,049.19	$1,049.10	$1,049.30