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	$213.65	3.664%	$221.4781	$221.48	$221.50	$221.50
Purchase #2	$158.93	5.152%	$167.1181	$167.12	$167.10	$167.10
Purchase #3	$207.50	7.280%	$222.606	$222.61	$222.60	$222.60
Purchase #4	$68.64	3.232%	$70.8584	$70.86	$70.85	$70.90
Purchase #5	$42.42	3.375%	$43.8517	$43.85	$43.85	$43.90
Purchase #6	$107.43	9.712%	$117.8636	$117.86	$117.85	$117.90
Purchase #7	$58.91	9.424%	$64.4617	$64.46	$64.45	$64.50
7 purchase totals =	$857.48		$908.2376	$908.24	$908.20	$908.40