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	$89.93	12.806%	$101.4464	$101.45	$101.45	$101.40
Purchase #2	$35.78	11.205%	$39.7891	$39.79	$39.80	$39.80
Purchase #3	$154.90	8.129%	$167.4918	$167.49	$167.50	$167.50
Purchase #4	$178.92	8.584%	$194.2785	$194.28	$194.30	$194.30
Purchase #5	$222.31	10.444%	$245.5281	$245.53	$245.55	$245.50
Purchase #6	$131.86	10.688%	$145.9532	$145.95	$145.95	$146.00
Purchase #7	$117.92	4.582%	$123.3231	$123.32	$123.30	$123.30
7 purchase totals =	$931.62		$1,017.8102	$1,017.81	$1,017.85	$1,017.80