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	$63.76	7.197%	$68.3488	$68.35	$68.35	$68.30
Purchase #2	$135.25	11.143%	$150.3209	$150.32	$150.30	$150.30
Purchase #3	$117.35	6.429%	$124.8944	$124.89	$124.90	$124.90
Purchase #4	$77.96	3.395%	$80.6067	$80.61	$80.60	$80.60
Purchase #5	$229.90	6.689%	$245.278	$245.28	$245.30	$245.30
Purchase #6	$156.74	11.564%	$174.8654	$174.87	$174.85	$174.90
Purchase #7	$99.80	12.513%	$112.288	$112.29	$112.30	$112.30
7 purchase totals =	$880.76		$956.6022	$956.61	$956.60	$956.60