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	$116.90	8.811%	$127.2001	$127.20	$127.20	$127.20
Purchase #2	$86.90	4.557%	$90.86	$90.86	$90.85	$90.90
Purchase #3	$80.78	9.286%	$88.2812	$88.28	$88.30	$88.30
Purchase #4	$162.79	3.741%	$168.88	$168.88	$168.90	$168.90
Purchase #5	$216.93	4.254%	$226.1582	$226.16	$226.15	$226.20
Purchase #6	$129.94	13.302%	$147.2246	$147.22	$147.20	$147.20
Purchase #7	$81.41	5.327%	$85.7467	$85.75	$85.75	$85.70
7 purchase totals =	$875.65		$934.3508	$934.35	$934.35	$934.40