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	$142.53	3.785%	$147.9248	$147.92	$147.90	$147.90
Purchase #2	$43.88	5.641%	$46.3553	$46.36	$46.35	$46.40
Purchase #3	$82.87	10.857%	$91.8672	$91.87	$91.85	$91.90
Purchase #4	$151.79	10.167%	$167.2225	$167.22	$167.20	$167.20
Purchase #5	$161.94	10.470%	$178.8951	$178.90	$178.90	$178.90
Purchase #6	$189.29	4.784%	$198.3456	$198.35	$198.35	$198.30
Purchase #7	$145.45	5.109%	$152.881	$152.88	$152.90	$152.90
7 purchase totals =	$917.75		$983.4915	$983.50	$983.45	$983.50