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	$113.50	12.648%	$127.8555	$127.86	$127.85	$127.90
Purchase #2	$29.72	8.526%	$32.2539	$32.25	$32.25	$32.30
Purchase #3	$139.57	5.618%	$147.411	$147.41	$147.40	$147.40
Purchase #4	$165.60	3.621%	$171.5964	$171.60	$171.60	$171.60
Purchase #5	$49.94	3.616%	$51.7458	$51.75	$51.75	$51.70
Purchase #6	$225.66	9.819%	$247.8176	$247.82	$247.80	$247.80
Purchase #7	$241.73	3.454%	$250.0794	$250.08	$250.10	$250.10
7 purchase totals =	$965.72		$1,028.7596	$1,028.77	$1,028.75	$1,028.80