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	$169.83	4.871%	$178.1024	$178.10	$178.10	$178.10
Purchase #2	$238.93	4.694%	$250.1454	$250.15	$250.15	$250.10
Purchase #3	$122.82	13.271%	$139.1194	$139.12	$139.10	$139.10
Purchase #4	$51.49	9.110%	$56.1807	$56.18	$56.20	$56.20
Purchase #5	$117.33	5.121%	$123.3385	$123.34	$123.35	$123.30
Purchase #6	$42.58	9.251%	$46.5191	$46.52	$46.50	$46.50
Purchase #7	$210.45	3.359%	$217.519	$217.52	$217.50	$217.50
7 purchase totals =	$953.43		$1,010.9245	$1,010.93	$1,010.90	$1,010.80