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	$192.36	3.714%	$199.5043	$199.50	$199.50	$199.50
Purchase #2	$202.40	6.432%	$215.4184	$215.42	$215.40	$215.40
Purchase #3	$73.28	11.360%	$81.6046	$81.60	$81.60	$81.60
Purchase #4	$234.69	8.386%	$254.3711	$254.37	$254.35	$254.40
Purchase #5	$212.63	5.121%	$223.5188	$223.52	$223.50	$223.50
Purchase #6	$43.78	3.437%	$45.2847	$45.28	$45.30	$45.30
Purchase #7	$172.57	13.167%	$195.2923	$195.29	$195.30	$195.30
7 purchase totals =	$1,131.71		$1,214.9942	$1,214.98	$1,214.95	$1,215.00