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	$229.48	9.171%	$250.5256	$250.53	$250.55	$250.50
Purchase #2	$76.38	11.836%	$85.4203	$85.42	$85.40	$85.40
Purchase #3	$198.87	6.332%	$211.4624	$211.46	$211.45	$211.50
Purchase #4	$45.66	9.264%	$49.8899	$49.89	$49.90	$49.90
Purchase #5	$171.30	7.112%	$183.4829	$183.48	$183.50	$183.50
Purchase #6	$162.92	9.561%	$178.4968	$178.50	$178.50	$178.50
Purchase #7	$74.89	4.763%	$78.457	$78.46	$78.45	$78.50
7 purchase totals =	$959.50		$1,037.7349	$1,037.74	$1,037.75	$1,037.80