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	$41.37	4.392%	$43.187	$43.19	$43.20	$43.20
Purchase #2	$92.56	4.168%	$96.4179	$96.42	$96.40	$96.40
Purchase #3	$25.29	7.617%	$27.2163	$27.22	$27.20	$27.20
Purchase #4	$85.46	5.534%	$90.1894	$90.19	$90.20	$90.20
Purchase #5	$209.25	6.451%	$222.7487	$222.75	$222.75	$222.70
Purchase #6	$49.82	8.649%	$54.1289	$54.13	$54.15	$54.10
Purchase #7	$74.79	7.642%	$80.5055	$80.51	$80.50	$80.50
7 purchase totals =	$578.54		$614.3937	$614.41	$614.40	$614.30