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	$130.71	5.296%	$137.6324	$137.63	$137.65	$137.60
Purchase #2	$73.58	5.617%	$77.713	$77.71	$77.70	$77.70
Purchase #3	$98.94	6.332%	$105.2049	$105.20	$105.20	$105.20
Purchase #4	$97.54	7.133%	$104.4975	$104.50	$104.50	$104.50
Purchase #5	$63.45	7.671%	$68.3172	$68.32	$68.30	$68.30
Purchase #6	$6.40	13.774%	$7.2815	$7.28	$7.30	$7.30
Purchase #7	$78.46	10.742%	$86.8882	$86.89	$86.90	$86.90
7 purchase totals =	$549.08		$587.5347	$587.53	$587.55	$587.50