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	$166.47	3.511%	$172.3148	$172.31	$172.30	$172.30
Purchase #2	$152.80	10.112%	$168.2511	$168.25	$168.25	$168.30
Purchase #3	$92.35	6.206%	$98.0812	$98.08	$98.10	$98.10
Purchase #4	$122.78	4.868%	$128.7569	$128.76	$128.75	$128.80
Purchase #5	$134.29	8.734%	$146.0189	$146.02	$146.00	$146.00
Purchase #6	$58.40	4.684%	$61.1355	$61.14	$61.15	$61.10
Purchase #7	$217.94	10.731%	$241.3271	$241.33	$241.35	$241.30
7 purchase totals =	$945.03		$1,015.8855	$1,015.89	$1,015.90	$1,015.90