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	$33.64	12.354%	$37.7959	$37.80	$37.80	$37.80
Purchase #2	$67.99	7.158%	$72.8567	$72.86	$72.85	$72.90
Purchase #3	$99.79	13.532%	$113.2936	$113.29	$113.30	$113.30
Purchase #4	$175.65	7.401%	$188.6499	$188.65	$188.65	$188.60
Purchase #5	$153.51	13.587%	$174.3674	$174.37	$174.35	$174.40
Purchase #6	$64.55	11.183%	$71.7686	$71.77	$71.75	$71.80
Purchase #7	$40.96	10.239%	$45.1539	$45.15	$45.15	$45.20
7 purchase totals =	$636.09		$703.8860	$703.89	$703.85	$704.00