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	$189.39	8.814%	$206.0828	$206.08	$206.10	$206.10
Purchase #2	$13.55	11.854%	$15.1562	$15.16	$15.15	$15.20
Purchase #3	$86.90	10.531%	$96.0514	$96.05	$96.05	$96.10
Purchase #4	$168.84	4.641%	$176.6759	$176.68	$176.70	$176.70
Purchase #5	$72.94	7.558%	$78.4528	$78.45	$78.45	$78.50
Purchase #6	$122.70	4.234%	$127.8951	$127.90	$127.90	$127.90
Purchase #7	$53.72	12.414%	$60.3888	$60.39	$60.40	$60.40
7 purchase totals =	$708.04		$760.7030	$760.71	$760.75	$760.90