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	$135.90	11.715%	$151.8207	$151.82	$151.80	$151.80
Purchase #2	$96.33	12.236%	$108.1169	$108.12	$108.10	$108.10
Purchase #3	$223.86	11.812%	$250.3023	$250.30	$250.30	$250.30
Purchase #4	$210.62	6.630%	$224.5841	$224.58	$224.60	$224.60
Purchase #5	$30.46	6.169%	$32.3391	$32.34	$32.35	$32.30
Purchase #6	$195.69	10.277%	$215.8011	$215.80	$215.80	$215.80
Purchase #7	$68.97	3.770%	$71.5702	$71.57	$71.55	$71.60
7 purchase totals =	$961.83		$1,054.5344	$1,054.53	$1,054.50	$1,054.50