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	$213.88	9.666%	$234.5536	$234.55	$234.55	$234.60
Purchase #2	$36.42	10.700%	$40.3169	$40.32	$40.30	$40.30
Purchase #3	$30.56	7.718%	$32.9186	$32.92	$32.90	$32.90
Purchase #4	$93.61	5.243%	$98.518	$98.52	$98.50	$98.50
Purchase #5	$177.44	12.120%	$198.9457	$198.95	$198.95	$198.90
Purchase #6	$178.79	11.525%	$199.3955	$199.40	$199.40	$199.40
Purchase #7	$190.55	4.169%	$198.494	$198.49	$198.50	$198.50
7 purchase totals =	$921.25		$1,003.1423	$1,003.15	$1,003.10	$1,003.10