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	$45.97	12.346%	$51.6455	$51.65	$51.65	$51.60
Purchase #2	$214.92	6.149%	$228.1354	$228.14	$228.15	$228.10
Purchase #3	$163.51	4.760%	$171.2931	$171.29	$171.30	$171.30
Purchase #4	$79.86	13.582%	$90.7066	$90.71	$90.70	$90.70
Purchase #5	$93.51	11.803%	$104.547	$104.55	$104.55	$104.50
Purchase #6	$56.36	7.454%	$60.5611	$60.56	$60.55	$60.60
Purchase #7	$140.59	10.443%	$155.2718	$155.27	$155.25	$155.30
7 purchase totals =	$794.72		$862.1605	$862.17	$862.15	$862.10