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	$33.69	8.826%	$36.6635	$36.66	$36.65	$36.70
Purchase #2	$167.73	4.710%	$175.6301	$175.63	$175.65	$175.60
Purchase #3	$62.60	5.148%	$65.8226	$65.82	$65.80	$65.80
Purchase #4	$143.77	5.762%	$152.054	$152.05	$152.05	$152.10
Purchase #5	$172.65	5.475%	$182.1026	$182.10	$182.10	$182.10
Purchase #6	$72.77	13.124%	$82.3203	$82.32	$82.30	$82.30
Purchase #7	$70.32	3.162%	$72.5435	$72.54	$72.55	$72.50
7 purchase totals =	$723.53		$767.1366	$767.12	$767.10	$767.10