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	$174.97	3.330%	$180.7965	$180.80	$180.80	$180.80
Purchase #2	$68.93	13.372%	$78.1473	$78.15	$78.15	$78.10
Purchase #3	$147.89	5.866%	$156.5652	$156.57	$156.55	$156.60
Purchase #4	$33.74	4.604%	$35.2934	$35.29	$35.30	$35.30
Purchase #5	$215.64	7.236%	$231.2437	$231.24	$231.25	$231.20
Purchase #6	$238.52	12.191%	$267.598	$267.60	$267.60	$267.60
Purchase #7	$61.56	5.141%	$64.7248	$64.72	$64.70	$64.70
7 purchase totals =	$941.25		$1,014.3689	$1,014.37	$1,014.35	$1,014.30