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	$224.67	3.802%	$233.212	$233.21	$233.20	$233.20
Purchase #2	$101.47	6.297%	$107.8596	$107.86	$107.85	$107.90
Purchase #3	$62.58	7.582%	$67.3248	$67.32	$67.30	$67.30
Purchase #4	$56.82	8.296%	$61.5338	$61.53	$61.55	$61.50
Purchase #5	$148.58	5.243%	$156.37	$156.37	$156.35	$156.40
Purchase #6	$223.83	12.165%	$251.0589	$251.06	$251.05	$251.10
Purchase #7	$183.33	6.156%	$194.6158	$194.62	$194.60	$194.60
7 purchase totals =	$1,001.28		$1,071.9749	$1,071.97	$1,071.90	$1,072.00