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	$156.63	3.817%	$162.6086	$162.61	$162.60	$162.60
Purchase #2	$126.73	4.391%	$132.2947	$132.29	$132.30	$132.30
Purchase #3	$27.80	10.648%	$30.7601	$30.76	$30.75	$30.80
Purchase #4	$23.56	10.224%	$25.9688	$25.97	$25.95	$26.00
Purchase #5	$172.31	13.873%	$196.2146	$196.21	$196.20	$196.20
Purchase #6	$181.27	8.397%	$196.4912	$196.49	$196.50	$196.50
Purchase #7	$85.46	11.526%	$95.3101	$95.31	$95.30	$95.30
7 purchase totals =	$773.76		$839.6481	$839.64	$839.60	$839.70