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	$56.63	5.362%	$59.6665	$59.67	$59.65	$59.70
Purchase #2	$239.85	6.106%	$254.4952	$254.50	$254.50	$254.50
Purchase #3	$91.96	4.262%	$95.8793	$95.88	$95.90	$95.90
Purchase #4	$101.44	4.454%	$105.9581	$105.96	$105.95	$106.00
Purchase #5	$98.35	13.864%	$111.9852	$111.99	$112.00	$112.00
Purchase #6	$116.27	10.720%	$128.7341	$128.73	$128.75	$128.70
Purchase #7	$121.40	7.212%	$130.1554	$130.16	$130.15	$130.20
7 purchase totals =	$825.90		$886.8738	$886.89	$886.90	$887.00