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	$83.31	3.736%	$86.4225	$86.42	$86.40	$86.40
Purchase #2	$246.35	12.188%	$276.3751	$276.38	$276.40	$276.40
Purchase #3	$41.32	4.361%	$43.122	$43.12	$43.10	$43.10
Purchase #4	$157.72	8.638%	$171.3439	$171.34	$171.35	$171.30
Purchase #5	$198.56	11.401%	$221.1978	$221.20	$221.20	$221.20
Purchase #6	$123.43	12.870%	$139.3154	$139.32	$139.30	$139.30
Purchase #7	$75.69	12.154%	$84.8894	$84.89	$84.90	$84.90
7 purchase totals =	$926.38		$1,022.6661	$1,022.67	$1,022.65	$1,022.60