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	$181.97	7.870%	$196.291	$196.29	$196.30	$196.30
Purchase #2	$150.46	3.209%	$155.2883	$155.29	$155.30	$155.30
Purchase #3	$162.77	13.337%	$184.4786	$184.48	$184.50	$184.50
Purchase #4	$145.51	10.854%	$161.3037	$161.30	$161.30	$161.30
Purchase #5	$136.50	11.423%	$152.0924	$152.09	$152.10	$152.10
Purchase #6	$130.28	9.578%	$142.7582	$142.76	$142.75	$142.80
Purchase #7	$196.63	10.586%	$217.4453	$217.45	$217.45	$217.40
7 purchase totals =	$1,104.12		$1,209.6575	$1,209.66	$1,209.70	$1,209.70