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	$148.57	4.326%	$154.9971	$155.00	$155.00	$155.00
Purchase #2	$127.73	6.654%	$136.2292	$136.23	$136.25	$136.20
Purchase #3	$41.56	5.558%	$43.8699	$43.87	$43.85	$43.90
Purchase #4	$239.62	13.270%	$271.4176	$271.42	$271.40	$271.40
Purchase #5	$80.62	3.610%	$83.5304	$83.53	$83.55	$83.50
Purchase #6	$158.48	9.767%	$173.9587	$173.96	$173.95	$174.00
Purchase #7	$218.72	5.601%	$230.9705	$230.97	$230.95	$231.00
7 purchase totals =	$1,015.30		$1,094.9734	$1,094.98	$1,094.95	$1,095.00