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	$50.30	11.573%	$56.1212	$56.12	$56.10	$56.10
Purchase #2	$17.72	6.601%	$18.8897	$18.89	$18.90	$18.90
Purchase #3	$93.93	7.658%	$101.1232	$101.12	$101.10	$101.10
Purchase #4	$203.51	3.721%	$211.0826	$211.08	$211.10	$211.10
Purchase #5	$238.55	7.637%	$256.7681	$256.77	$256.75	$256.80
Purchase #6	$82.30	9.688%	$90.2732	$90.27	$90.25	$90.30
Purchase #7	$249.51	7.814%	$269.0067	$269.01	$269.00	$269.00
7 purchase totals =	$935.82		$1,003.2647	$1,003.26	$1,003.20	$1,003.30