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	$167.84	10.633%	$185.6864	$185.69	$185.70	$185.70
Purchase #2	$196.32	13.216%	$222.2657	$222.27	$222.25	$222.30
Purchase #3	$139.37	8.487%	$151.1983	$151.20	$151.20	$151.20
Purchase #4	$100.32	6.119%	$106.4586	$106.46	$106.45	$106.50
Purchase #5	$240.88	8.673%	$261.7715	$261.77	$261.75	$261.80
Purchase #6	$60.70	11.768%	$67.8432	$67.84	$67.85	$67.80
Purchase #7	$162.93	8.770%	$177.219	$177.22	$177.20	$177.20
7 purchase totals =	$1,068.36		$1,172.4427	$1,172.45	$1,172.40	$1,172.50