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	$90.81	10.501%	$100.346	$100.35	$100.35	$100.30
Purchase #2	$223.37	4.369%	$233.129	$233.13	$233.15	$233.10
Purchase #3	$8.42	5.816%	$8.9097	$8.91	$8.90	$8.90
Purchase #4	$57.92	12.661%	$65.2533	$65.25	$65.25	$65.30
Purchase #5	$226.76	6.382%	$241.2318	$241.23	$241.25	$241.20
Purchase #6	$201.72	10.356%	$222.6101	$222.61	$222.60	$222.60
Purchase #7	$96.42	7.690%	$103.8347	$103.83	$103.85	$103.80
7 purchase totals =	$905.42		$975.3146	$975.31	$975.35	$975.20