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	$90.28	8.380%	$97.8455	$97.85	$97.85	$97.80
Purchase #2	$171.81	6.140%	$182.3591	$182.36	$182.35	$182.40
Purchase #3	$18.89	7.457%	$20.2986	$20.30	$20.30	$20.30
Purchase #4	$232.51	12.851%	$262.3899	$262.39	$262.40	$262.40
Purchase #5	$129.54	7.544%	$139.3125	$139.31	$139.30	$139.30
Purchase #6	$206.81	10.384%	$228.2852	$228.29	$228.30	$228.30
Purchase #7	$241.55	6.320%	$256.816	$256.82	$256.80	$256.80
7 purchase totals =	$1,091.39		$1,187.3068	$1,187.32	$1,187.30	$1,187.30