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	$181.83	4.874%	$190.6924	$190.69	$190.70	$190.70
Purchase #2	$225.78	3.762%	$234.2738	$234.27	$234.25	$234.30
Purchase #3	$217.54	9.538%	$238.289	$238.29	$238.30	$238.30
Purchase #4	$242.83	6.264%	$258.0409	$258.04	$258.05	$258.00
Purchase #5	$184.73	13.203%	$209.1199	$209.12	$209.10	$209.10
Purchase #6	$41.94	3.399%	$43.3655	$43.37	$43.35	$43.40
Purchase #7	$125.33	7.253%	$134.4202	$134.42	$134.40	$134.40
7 purchase totals =	$1,219.98		$1,308.2017	$1,308.20	$1,308.15	$1,308.20