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	$61.67	10.424%	$68.0985	$68.10	$68.10	$68.10
Purchase #2	$42.89	6.430%	$45.6478	$45.65	$45.65	$45.60
Purchase #3	$92.46	8.499%	$100.3182	$100.32	$100.30	$100.30
Purchase #4	$220.56	5.314%	$232.2806	$232.28	$232.30	$232.30
Purchase #5	$220.52	6.408%	$234.6509	$234.65	$234.65	$234.70
Purchase #6	$216.48	5.561%	$228.5185	$228.52	$228.50	$228.50
Purchase #7	$156.36	12.453%	$175.8315	$175.83	$175.85	$175.80
7 purchase totals =	$1,010.94		$1,085.3460	$1,085.35	$1,085.35	$1,085.30