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	$58.27	4.815%	$61.0757	$61.08	$61.10	$61.10
Purchase #2	$200.83	9.300%	$219.5072	$219.51	$219.50	$219.50
Purchase #3	$31.77	11.784%	$35.5138	$35.51	$35.50	$35.50
Purchase #4	$71.74	4.383%	$74.8844	$74.88	$74.90	$74.90
Purchase #5	$119.48	11.539%	$133.2668	$133.27	$133.25	$133.30
Purchase #6	$139.87	3.300%	$144.4857	$144.49	$144.50	$144.50
Purchase #7	$201.82	3.236%	$208.3509	$208.35	$208.35	$208.40
7 purchase totals =	$823.78		$877.0845	$877.09	$877.10	$877.20