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	$204.40	7.285%	$219.2905	$219.29	$219.30	$219.30
Purchase #2	$185.37	5.121%	$194.8628	$194.86	$194.85	$194.90
Purchase #3	$236.57	9.437%	$258.8951	$258.90	$258.90	$258.90
Purchase #4	$201.30	8.678%	$218.7688	$218.77	$218.75	$218.80
Purchase #5	$120.57	5.738%	$127.4883	$127.49	$127.50	$127.50
Purchase #6	$73.80	4.777%	$77.3254	$77.33	$77.35	$77.30
Purchase #7	$143.78	13.290%	$162.8884	$162.89	$162.90	$162.90
7 purchase totals =	$1,165.79		$1,259.5193	$1,259.53	$1,259.55	$1,259.60