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	$78.26	13.203%	$88.5927	$88.59	$88.60	$88.60
Purchase #2	$18.69	3.453%	$19.3354	$19.34	$19.35	$19.30
Purchase #3	$90.37	5.131%	$95.0069	$95.01	$95.00	$95.00
Purchase #4	$69.40	12.552%	$78.1111	$78.11	$78.10	$78.10
Purchase #5	$175.94	5.862%	$186.2536	$186.25	$186.25	$186.30
Purchase #6	$177.40	4.459%	$185.3103	$185.31	$185.30	$185.30
Purchase #7	$128.42	5.530%	$135.5216	$135.52	$135.50	$135.50
7 purchase totals =	$738.48		$788.1316	$788.13	$788.10	$788.10