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	$49.94	4.405%	$52.1399	$52.14	$52.15	$52.10
Purchase #2	$176.89	13.379%	$200.5561	$200.56	$200.55	$200.60
Purchase #3	$81.92	11.799%	$91.5857	$91.59	$91.60	$91.60
Purchase #4	$67.80	12.199%	$76.0709	$76.07	$76.05	$76.10
Purchase #5	$80.92	3.251%	$83.5507	$83.55	$83.55	$83.60
Purchase #6	$168.85	7.414%	$181.3685	$181.37	$181.35	$181.40
Purchase #7	$62.77	11.828%	$70.1944	$70.19	$70.20	$70.20
7 purchase totals =	$689.09		$755.4662	$755.47	$755.45	$755.60