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	$121.60	4.706%	$127.3225	$127.32	$127.30	$127.30
Purchase #2	$105.79	6.403%	$112.5637	$112.56	$112.55	$112.60
Purchase #3	$196.68	6.651%	$209.7612	$209.76	$209.75	$209.80
Purchase #4	$224.32	11.770%	$250.7225	$250.72	$250.70	$250.70
Purchase #5	$55.59	10.260%	$61.2935	$61.29	$61.30	$61.30
Purchase #6	$164.26	8.468%	$178.1695	$178.17	$178.15	$178.20
Purchase #7	$167.98	8.847%	$182.8412	$182.84	$182.85	$182.80
7 purchase totals =	$1,036.22		$1,122.6741	$1,122.66	$1,122.60	$1,122.70