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	$113.73	5.155%	$119.5928	$119.59	$119.60	$119.60
Purchase #2	$121.28	8.132%	$131.1425	$131.14	$131.15	$131.10
Purchase #3	$66.85	6.185%	$70.9847	$70.98	$71.00	$71.00
Purchase #4	$111.51	3.623%	$115.55	$115.55	$115.55	$115.60
Purchase #5	$179.55	9.675%	$196.9215	$196.92	$196.90	$196.90
Purchase #6	$22.34	4.435%	$23.3308	$23.33	$23.35	$23.30
Purchase #7	$70.40	6.405%	$74.9091	$74.91	$74.90	$74.90
7 purchase totals =	$685.66		$732.4314	$732.42	$732.45	$732.40