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	$187.89	4.738%	$196.7922	$196.79	$196.80	$196.80
Purchase #2	$177.36	9.593%	$194.3741	$194.37	$194.35	$194.40
Purchase #3	$130.61	10.399%	$144.1921	$144.19	$144.20	$144.20
Purchase #4	$88.59	5.630%	$93.5776	$93.58	$93.60	$93.60
Purchase #5	$29.32	6.188%	$31.1343	$31.13	$31.15	$31.10
Purchase #6	$242.72	13.722%	$276.026	$276.03	$276.05	$276.00
Purchase #7	$136.43	3.482%	$141.1805	$141.18	$141.20	$141.20
7 purchase totals =	$992.92		$1,077.2768	$1,077.27	$1,077.35	$1,077.30