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	$163.56	10.401%	$180.5719	$180.57	$180.55	$180.60
Purchase #2	$160.99	5.644%	$170.0763	$170.08	$170.10	$170.10
Purchase #3	$91.33	9.176%	$99.7104	$99.71	$99.70	$99.70
Purchase #4	$177.59	5.473%	$187.3095	$187.31	$187.30	$187.30
Purchase #5	$19.61	13.130%	$22.1848	$22.18	$22.20	$22.20
Purchase #6	$196.44	10.623%	$217.3078	$217.31	$217.30	$217.30
Purchase #7	$131.84	5.689%	$139.3404	$139.34	$139.35	$139.30
7 purchase totals =	$941.36		$1,016.5011	$1,016.50	$1,016.50	$1,016.50