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	$39.94	13.132%	$45.1849	$45.18	$45.20	$45.20
Purchase #2	$162.88	3.410%	$168.4342	$168.43	$168.45	$168.40
Purchase #3	$29.90	3.713%	$31.0102	$31.01	$31.00	$31.00
Purchase #4	$187.74	4.361%	$195.9273	$195.93	$195.95	$195.90
Purchase #5	$117.50	8.231%	$127.1714	$127.17	$127.15	$127.20
Purchase #6	$54.39	10.530%	$60.1173	$60.12	$60.10	$60.10
Purchase #7	$97.26	13.372%	$110.2656	$110.27	$110.25	$110.30
7 purchase totals =	$689.61		$738.1109	$738.11	$738.10	$738.10