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	$64.91	13.537%	$73.6969	$73.70	$73.70	$73.70
Purchase #2	$127.29	3.402%	$131.6204	$131.62	$131.60	$131.60
Purchase #3	$154.46	8.675%	$167.8594	$167.86	$167.85	$167.90
Purchase #4	$182.40	6.601%	$194.4402	$194.44	$194.45	$194.40
Purchase #5	$84.83	12.459%	$95.399	$95.40	$95.40	$95.40
Purchase #6	$161.76	7.619%	$174.0845	$174.08	$174.10	$174.10
Purchase #7	$40.27	12.770%	$45.4125	$45.41	$45.40	$45.40
7 purchase totals =	$815.92		$882.5129	$882.51	$882.50	$882.50