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	$93.57	9.102%	$102.0867	$102.09	$102.10	$102.10
Purchase #2	$98.28	10.182%	$108.2869	$108.29	$108.30	$108.30
Purchase #3	$247.36	5.461%	$260.8683	$260.87	$260.85	$260.90
Purchase #4	$245.54	4.609%	$256.8569	$256.86	$256.85	$256.90
Purchase #5	$123.90	4.569%	$129.561	$129.56	$129.55	$129.60
Purchase #6	$88.72	3.503%	$91.8279	$91.83	$91.85	$91.80
Purchase #7	$51.35	7.276%	$55.0862	$55.09	$55.10	$55.10
7 purchase totals =	$948.72		$1,004.5739	$1,004.59	$1,004.60	$1,004.70