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	$143.93	11.535%	$160.5323	$160.53	$160.55	$160.50
Purchase #2	$180.49	5.193%	$189.8628	$189.86	$189.85	$189.90
Purchase #3	$166.91	6.350%	$177.5088	$177.51	$177.50	$177.50
Purchase #4	$147.59	4.516%	$154.2552	$154.26	$154.25	$154.30
Purchase #5	$98.31	11.803%	$109.9135	$109.91	$109.90	$109.90
Purchase #6	$143.33	5.583%	$151.3321	$151.33	$151.35	$151.30
Purchase #7	$194.52	12.470%	$218.7766	$218.78	$218.80	$218.80
7 purchase totals =	$1,075.08		$1,162.1813	$1,162.18	$1,162.20	$1,162.20