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	$212.76	6.844%	$227.3213	$227.32	$227.30	$227.30
Purchase #2	$162.85	7.320%	$174.7706	$174.77	$174.75	$174.80
Purchase #3	$48.34	11.477%	$53.888	$53.89	$53.90	$53.90
Purchase #4	$18.87	5.712%	$19.9479	$19.95	$19.95	$19.90
Purchase #5	$234.30	13.866%	$266.788	$266.79	$266.80	$266.80
Purchase #6	$89.29	10.442%	$98.6137	$98.61	$98.60	$98.60
Purchase #7	$146.60	13.791%	$166.8176	$166.82	$166.80	$166.80
7 purchase totals =	$913.01		$1,008.1471	$1,008.15	$1,008.10	$1,008.10