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	$243.90	7.466%	$262.1096	$262.11	$262.10	$262.10
Purchase #2	$49.60	9.839%	$54.4801	$54.48	$54.50	$54.50
Purchase #3	$236.81	3.232%	$244.4637	$244.46	$244.45	$244.50
Purchase #4	$115.40	10.464%	$127.4755	$127.48	$127.50	$127.50
Purchase #5	$168.70	9.453%	$184.6472	$184.65	$184.65	$184.60
Purchase #6	$50.34	11.717%	$56.2383	$56.24	$56.25	$56.20
Purchase #7	$108.25	9.378%	$118.4017	$118.40	$118.40	$118.40
7 purchase totals =	$973.00		$1,047.8161	$1,047.82	$1,047.85	$1,047.80