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	$224.93	5.433%	$237.1504	$237.15	$237.15	$237.20
Purchase #2	$55.78	10.296%	$61.5231	$61.52	$61.50	$61.50
Purchase #3	$184.66	6.357%	$196.3988	$196.40	$196.40	$196.40
Purchase #4	$158.91	3.369%	$164.2637	$164.26	$164.25	$164.30
Purchase #5	$49.87	11.542%	$55.626	$55.63	$55.65	$55.60
Purchase #6	$104.68	4.240%	$109.1184	$109.12	$109.10	$109.10
Purchase #7	$150.47	8.290%	$162.944	$162.94	$162.95	$162.90
7 purchase totals =	$929.30		$987.0244	$987.02	$987.00	$987.00