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	$170.98	5.178%	$179.8333	$179.83	$179.85	$179.80
Purchase #2	$214.63	4.160%	$223.5586	$223.56	$223.55	$223.60
Purchase #3	$104.35	7.276%	$111.9425	$111.94	$111.95	$111.90
Purchase #4	$109.94	5.424%	$115.9031	$115.90	$115.90	$115.90
Purchase #5	$159.86	5.866%	$169.2374	$169.24	$169.25	$169.20
Purchase #6	$193.81	13.461%	$219.8988	$219.90	$219.90	$219.90
Purchase #7	$162.96	9.342%	$178.1837	$178.18	$178.20	$178.20
7 purchase totals =	$1,116.53		$1,198.5574	$1,198.55	$1,198.60	$1,198.50