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	$198.84	11.655%	$222.0148	$222.01	$222.00	$222.00
Purchase #2	$118.64	7.593%	$127.6483	$127.65	$127.65	$127.60
Purchase #3	$117.55	6.616%	$125.3271	$125.33	$125.35	$125.30
Purchase #4	$86.60	4.306%	$90.329	$90.33	$90.35	$90.30
Purchase #5	$164.56	10.659%	$182.1005	$182.10	$182.10	$182.10
Purchase #6	$172.60	3.195%	$178.1146	$178.11	$178.10	$178.10
Purchase #7	$50.52	9.440%	$55.2891	$55.29	$55.30	$55.30
7 purchase totals =	$909.31		$980.8234	$980.82	$980.85	$980.70