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	$179.41	6.414%	$190.9174	$190.92	$190.90	$190.90
Purchase #2	$127.57	7.125%	$136.6594	$136.66	$136.65	$136.70
Purchase #3	$49.27	12.638%	$55.4967	$55.50	$55.50	$55.50
Purchase #4	$165.28	8.105%	$178.6759	$178.68	$178.70	$178.70
Purchase #5	$213.87	12.707%	$241.0465	$241.05	$241.05	$241.00
Purchase #6	$54.37	6.199%	$57.7404	$57.74	$57.75	$57.70
Purchase #7	$148.82	10.511%	$164.4625	$164.46	$164.45	$164.50
7 purchase totals =	$938.59		$1,024.9988	$1,025.01	$1,025.00	$1,025.00