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	$101.46	12.377%	$114.0177	$114.02	$114.00	$114.00
Purchase #2	$132.28	7.600%	$142.3333	$142.33	$142.35	$142.30
Purchase #3	$110.34	4.155%	$114.9246	$114.92	$114.90	$114.90
Purchase #4	$29.82	12.501%	$33.5478	$33.55	$33.55	$33.50
Purchase #5	$9.86	6.675%	$10.5182	$10.52	$10.50	$10.50
Purchase #6	$209.76	6.476%	$223.3441	$223.34	$223.35	$223.30
Purchase #7	$9.72	9.159%	$10.6103	$10.61	$10.60	$10.60
7 purchase totals =	$603.24		$649.2960	$649.29	$649.25	$649.10