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	$68.55	5.191%	$72.1084	$72.11	$72.10	$72.10
Purchase #2	$249.39	6.387%	$265.3185	$265.32	$265.30	$265.30
Purchase #3	$169.40	11.395%	$188.7031	$188.70	$188.70	$188.70
Purchase #4	$5.80	3.114%	$5.9806	$5.98	$6.00	$6.00
Purchase #5	$56.37	6.169%	$59.8475	$59.85	$59.85	$59.80
Purchase #6	$74.73	5.612%	$78.9238	$78.92	$78.90	$78.90
Purchase #7	$241.67	12.297%	$271.3882	$271.39	$271.40	$271.40
7 purchase totals =	$865.91		$942.2701	$942.27	$942.25	$942.20