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	$143.32	6.628%	$152.8192	$152.82	$152.80	$152.80
Purchase #2	$196.34	10.383%	$216.726	$216.73	$216.75	$216.70
Purchase #3	$242.93	4.169%	$253.0578	$253.06	$253.05	$253.10
Purchase #4	$154.84	9.534%	$169.6024	$169.60	$169.60	$169.60
Purchase #5	$139.59	9.276%	$152.5384	$152.54	$152.55	$152.50
Purchase #6	$203.94	12.555%	$229.5447	$229.54	$229.55	$229.50
Purchase #7	$80.82	10.869%	$89.6043	$89.60	$89.60	$89.60
7 purchase totals =	$1,161.78		$1,263.8928	$1,263.89	$1,263.90	$1,263.80