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	$168.69	13.385%	$191.2692	$191.27	$191.25	$191.30
Purchase #2	$83.46	8.796%	$90.8011	$90.80	$90.80	$90.80
Purchase #3	$224.50	11.117%	$249.4577	$249.46	$249.45	$249.50
Purchase #4	$138.28	9.280%	$151.1124	$151.11	$151.10	$151.10
Purchase #5	$39.59	10.511%	$43.7513	$43.75	$43.75	$43.80
Purchase #6	$88.66	13.782%	$100.8791	$100.88	$100.90	$100.90
Purchase #7	$178.41	3.570%	$184.7792	$184.78	$184.80	$184.80
7 purchase totals =	$921.59		$1,012.0500	$1,012.05	$1,012.05	$1,012.20