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	$118.39	4.287%	$123.4654	$123.47	$123.45	$123.50
Purchase #2	$48.25	7.693%	$51.9619	$51.96	$51.95	$52.00
Purchase #3	$30.26	10.707%	$33.4999	$33.50	$33.50	$33.50
Purchase #4	$35.75	12.808%	$40.3289	$40.33	$40.35	$40.30
Purchase #5	$204.55	3.596%	$211.9056	$211.91	$211.90	$211.90
Purchase #6	$220.88	3.825%	$229.3287	$229.33	$229.35	$229.30
Purchase #7	$185.94	3.230%	$191.9459	$191.95	$191.95	$191.90
7 purchase totals =	$844.02		$882.4363	$882.45	$882.45	$882.40