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	$72.84	13.626%	$82.7652	$82.77	$82.75	$82.80
Purchase #2	$125.64	4.622%	$131.4471	$131.45	$131.45	$131.40
Purchase #3	$6.80	12.727%	$7.6654	$7.67	$7.65	$7.70
Purchase #4	$233.93	7.355%	$251.1356	$251.14	$251.15	$251.10
Purchase #5	$95.84	9.784%	$105.217	$105.22	$105.20	$105.20
Purchase #6	$89.26	13.199%	$101.0414	$101.04	$101.05	$101.00
Purchase #7	$13.97	4.571%	$14.6086	$14.61	$14.60	$14.60
7 purchase totals =	$638.28		$693.8803	$693.90	$693.85	$693.80