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	$213.54	11.844%	$238.8317	$238.83	$238.85	$238.80
Purchase #2	$36.99	9.272%	$40.4197	$40.42	$40.40	$40.40
Purchase #3	$163.34	8.253%	$176.8205	$176.82	$176.80	$176.80
Purchase #4	$239.42	4.786%	$250.8786	$250.88	$250.90	$250.90
Purchase #5	$174.31	12.516%	$196.1266	$196.13	$196.15	$196.10
Purchase #6	$95.35	12.104%	$106.8912	$106.89	$106.90	$106.90
Purchase #7	$34.41	8.633%	$37.3806	$37.38	$37.40	$37.40
7 purchase totals =	$957.36		$1,047.3489	$1,047.35	$1,047.40	$1,047.30