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	$188.53	6.242%	$200.298	$200.30	$200.30	$200.30
Purchase #2	$13.37	6.216%	$14.2011	$14.20	$14.20	$14.20
Purchase #3	$129.71	13.864%	$147.693	$147.69	$147.70	$147.70
Purchase #4	$104.45	7.191%	$111.961	$111.96	$111.95	$112.00
Purchase #5	$208.33	5.187%	$219.1361	$219.14	$219.15	$219.10
Purchase #6	$99.31	12.406%	$111.6304	$111.63	$111.65	$111.60
Purchase #7	$107.70	5.462%	$113.5826	$113.58	$113.60	$113.60
7 purchase totals =	$851.40		$918.5022	$918.50	$918.55	$918.50