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	$102.75	5.229%	$108.1228	$108.12	$108.10	$108.10
Purchase #2	$42.39	7.530%	$45.582	$45.58	$45.60	$45.60
Purchase #3	$227.25	9.533%	$248.9137	$248.91	$248.90	$248.90
Purchase #4	$52.62	13.870%	$59.9184	$59.92	$59.90	$59.90
Purchase #5	$188.96	8.814%	$205.6149	$205.61	$205.60	$205.60
Purchase #6	$106.76	6.340%	$113.5286	$113.53	$113.55	$113.50
Purchase #7	$219.72	6.749%	$234.5489	$234.55	$234.55	$234.50
7 purchase totals =	$940.45		$1,016.2293	$1,016.22	$1,016.20	$1,016.10