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	$209.91	8.812%	$228.4073	$228.41	$228.40	$228.40
Purchase #2	$206.55	13.486%	$234.4053	$234.41	$234.40	$234.40
Purchase #3	$107.81	3.189%	$111.2481	$111.25	$111.25	$111.20
Purchase #4	$245.85	5.789%	$260.0823	$260.08	$260.10	$260.10
Purchase #5	$131.71	9.567%	$144.3107	$144.31	$144.30	$144.30
Purchase #6	$105.71	13.817%	$120.316	$120.32	$120.30	$120.30
Purchase #7	$31.72	5.818%	$33.5655	$33.57	$33.55	$33.60
7 purchase totals =	$1,039.26		$1,132.3352	$1,132.35	$1,132.30	$1,132.30