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	$8.60	7.586%	$9.2524	$9.25	$9.25	$9.30
Purchase #2	$11.51	7.123%	$12.3299	$12.33	$12.35	$12.30
Purchase #3	$120.46	9.538%	$131.9495	$131.95	$131.95	$131.90
Purchase #4	$25.92	9.614%	$28.4119	$28.41	$28.40	$28.40
Purchase #5	$104.89	8.832%	$114.1539	$114.15	$114.15	$114.20
Purchase #6	$110.30	3.842%	$114.5377	$114.54	$114.55	$114.50
Purchase #7	$74.78	11.602%	$83.456	$83.46	$83.45	$83.50
7 purchase totals =	$456.46		$494.0913	$494.09	$494.10	$494.10