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	$158.40	13.349%	$179.5448	$179.54	$179.55	$179.50
Purchase #2	$174.69	9.833%	$191.8673	$191.87	$191.85	$191.90
Purchase #3	$127.58	3.139%	$131.5847	$131.58	$131.60	$131.60
Purchase #4	$180.39	6.244%	$191.6536	$191.65	$191.65	$191.70
Purchase #5	$175.57	9.854%	$192.8707	$192.87	$192.85	$192.90
Purchase #6	$80.63	6.117%	$85.5621	$85.56	$85.55	$85.60
Purchase #7	$207.85	5.648%	$219.5894	$219.59	$219.60	$219.60
7 purchase totals =	$1,105.11		$1,192.6726	$1,192.66	$1,192.65	$1,192.80