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	$87.82	9.111%	$95.8213	$95.82	$95.80	$95.80
Purchase #2	$82.98	5.865%	$87.8468	$87.85	$87.85	$87.80
Purchase #3	$219.63	10.494%	$242.678	$242.68	$242.70	$242.70
Purchase #4	$182.71	4.709%	$191.3138	$191.31	$191.30	$191.30
Purchase #5	$202.81	5.426%	$213.8145	$213.81	$213.80	$213.80
Purchase #6	$125.78	4.227%	$131.0967	$131.10	$131.10	$131.10
Purchase #7	$105.95	8.448%	$114.9007	$114.90	$114.90	$114.90
7 purchase totals =	$1,007.68		$1,077.4718	$1,077.47	$1,077.45	$1,077.40