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	$219.72	6.383%	$233.7447	$233.74	$233.75	$233.70
Purchase #2	$184.63	6.554%	$196.7307	$196.73	$196.75	$196.70
Purchase #3	$204.70	8.465%	$222.0279	$222.03	$222.05	$222.00
Purchase #4	$101.28	4.311%	$105.6462	$105.65	$105.65	$105.60
Purchase #5	$113.74	6.359%	$120.9727	$120.97	$120.95	$121.00
Purchase #6	$248.86	11.864%	$278.3848	$278.38	$278.40	$278.40
Purchase #7	$239.92	8.162%	$259.5023	$259.50	$259.50	$259.50
7 purchase totals =	$1,312.85		$1,417.0093	$1,417.00	$1,417.05	$1,416.90