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	$181.51	7.329%	$194.8129	$194.81	$194.80	$194.80
Purchase #2	$107.79	3.603%	$111.6737	$111.67	$111.65	$111.70
Purchase #3	$5.57	5.247%	$5.8623	$5.86	$5.85	$5.90
Purchase #4	$66.35	4.366%	$69.2468	$69.25	$69.25	$69.20
Purchase #5	$208.76	3.843%	$216.7826	$216.78	$216.80	$216.80
Purchase #6	$109.97	12.640%	$123.8702	$123.87	$123.85	$123.90
Purchase #7	$112.51	4.135%	$117.1623	$117.16	$117.15	$117.20
7 purchase totals =	$792.46		$839.4108	$839.40	$839.35	$839.50