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	$124.53	3.391%	$128.7528	$128.75	$128.75	$128.80
Purchase #2	$9.89	10.627%	$10.941	$10.94	$10.95	$10.90
Purchase #3	$121.90	4.224%	$127.0491	$127.05	$127.05	$127.00
Purchase #4	$28.88	3.612%	$29.9231	$29.92	$29.90	$29.90
Purchase #5	$92.60	10.790%	$102.5915	$102.59	$102.60	$102.60
Purchase #6	$105.72	11.362%	$117.7319	$117.73	$117.75	$117.70
Purchase #7	$202.95	9.542%	$222.3155	$222.32	$222.30	$222.30
7 purchase totals =	$686.47		$739.3049	$739.30	$739.30	$739.20