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	$127.44	11.501%	$142.0969	$142.10	$142.10	$142.10
Purchase #2	$103.92	5.769%	$109.9151	$109.92	$109.90	$109.90
Purchase #3	$20.53	12.862%	$23.1706	$23.17	$23.15	$23.20
Purchase #4	$107.74	4.236%	$112.3039	$112.30	$112.30	$112.30
Purchase #5	$12.48	3.707%	$12.9426	$12.94	$12.95	$12.90
Purchase #6	$21.83	4.293%	$22.7672	$22.77	$22.75	$22.80
Purchase #7	$56.52	8.113%	$61.1055	$61.11	$61.10	$61.10
7 purchase totals =	$450.46		$484.3018	$484.31	$484.25	$484.30