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	$193.29	11.511%	$215.5396	$215.54	$215.55	$215.50
Purchase #2	$214.82	13.148%	$243.0645	$243.06	$243.05	$243.10
Purchase #3	$120.54	5.704%	$127.4156	$127.42	$127.40	$127.40
Purchase #4	$229.64	3.485%	$237.643	$237.64	$237.65	$237.60
Purchase #5	$95.74	9.552%	$104.8851	$104.89	$104.90	$104.90
Purchase #6	$43.55	11.153%	$48.4071	$48.41	$48.40	$48.40
Purchase #7	$91.41	8.147%	$98.8572	$98.86	$98.85	$98.90
7 purchase totals =	$988.99		$1,075.8121	$1,075.82	$1,075.80	$1,075.80