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	$136.64	10.199%	$150.5759	$150.58	$150.60	$150.60
Purchase #2	$214.33	4.577%	$224.1399	$224.14	$224.15	$224.10
Purchase #3	$120.76	11.674%	$134.8575	$134.86	$134.85	$134.90
Purchase #4	$59.59	5.658%	$62.9616	$62.96	$62.95	$63.00
Purchase #5	$27.78	7.687%	$29.9154	$29.92	$29.90	$29.90
Purchase #6	$88.89	3.476%	$91.9798	$91.98	$92.00	$92.00
Purchase #7	$42.88	5.716%	$45.331	$45.33	$45.35	$45.30
7 purchase totals =	$690.87		$739.7611	$739.77	$739.80	$739.80