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	$155.50	4.518%	$162.5255	$162.53	$162.55	$162.50
Purchase #2	$34.31	7.511%	$36.887	$36.89	$36.90	$36.90
Purchase #3	$80.28	12.561%	$90.364	$90.36	$90.35	$90.40
Purchase #4	$31.37	10.127%	$34.5468	$34.55	$34.55	$34.50
Purchase #5	$28.53	13.869%	$32.4868	$32.49	$32.50	$32.50
Purchase #6	$123.59	3.351%	$127.7315	$127.73	$127.75	$127.70
Purchase #7	$94.60	11.512%	$105.4904	$105.49	$105.50	$105.50
7 purchase totals =	$548.18		$590.0320	$590.04	$590.10	$590.00