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	$89.46	13.259%	$101.3215	$101.32	$101.30	$101.30
Purchase #2	$207.80	10.181%	$228.9561	$228.96	$228.95	$229.00
Purchase #3	$135.31	11.347%	$150.6636	$150.66	$150.65	$150.70
Purchase #4	$181.51	3.232%	$187.3764	$187.38	$187.40	$187.40
Purchase #5	$211.59	13.811%	$240.8127	$240.81	$240.80	$240.80
Purchase #6	$93.78	11.502%	$104.5666	$104.57	$104.55	$104.60
Purchase #7	$28.51	12.587%	$32.0986	$32.10	$32.10	$32.10
7 purchase totals =	$947.96		$1,045.7955	$1,045.80	$1,045.75	$1,045.90