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	$82.57	6.178%	$87.6712	$87.67	$87.65	$87.70
Purchase #2	$39.96	12.784%	$45.0685	$45.07	$45.05	$45.10
Purchase #3	$47.41	7.224%	$50.8349	$50.83	$50.85	$50.80
Purchase #4	$54.76	3.783%	$56.8316	$56.83	$56.85	$56.80
Purchase #5	$239.82	5.529%	$253.0796	$253.08	$253.10	$253.10
Purchase #6	$164.82	4.660%	$172.5006	$172.50	$172.50	$172.50
Purchase #7	$60.86	3.316%	$62.8781	$62.88	$62.90	$62.90
7 purchase totals =	$690.20		$728.8645	$728.86	$728.90	$728.90