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	$79.44	3.367%	$82.1147	$82.11	$82.10	$82.10
Purchase #2	$58.67	4.187%	$61.1265	$61.13	$61.15	$61.10
Purchase #3	$76.42	5.157%	$80.361	$80.36	$80.35	$80.40
Purchase #4	$94.74	9.395%	$103.6408	$103.64	$103.65	$103.60
Purchase #5	$85.98	13.851%	$97.8891	$97.89	$97.90	$97.90
Purchase #6	$168.93	12.581%	$190.1831	$190.18	$190.20	$190.20
Purchase #7	$101.30	10.827%	$112.2678	$112.27	$112.25	$112.30
7 purchase totals =	$665.48		$727.5830	$727.58	$727.60	$727.60