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	$69.42	10.254%	$76.5383	$76.54	$76.55	$76.50
Purchase #2	$167.35	7.269%	$179.5147	$179.51	$179.50	$179.50
Purchase #3	$94.88	12.632%	$106.8652	$106.87	$106.85	$106.90
Purchase #4	$152.32	11.160%	$169.3189	$169.32	$169.30	$169.30
Purchase #5	$160.85	4.169%	$167.5558	$167.56	$167.55	$167.60
Purchase #6	$216.59	5.425%	$228.34	$228.34	$228.35	$228.30
Purchase #7	$55.74	9.235%	$60.8876	$60.89	$60.90	$60.90
7 purchase totals =	$917.15		$989.0205	$989.03	$989.00	$989.00