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	$232.87	13.410%	$264.0979	$264.10	$264.10	$264.10
Purchase #2	$77.58	7.283%	$83.2302	$83.23	$83.25	$83.20
Purchase #3	$49.52	13.670%	$56.2894	$56.29	$56.30	$56.30
Purchase #4	$90.33	7.214%	$96.8464	$96.85	$96.85	$96.80
Purchase #5	$208.86	12.471%	$234.9069	$234.91	$234.90	$234.90
Purchase #6	$131.25	4.831%	$137.5907	$137.59	$137.60	$137.60
Purchase #7	$166.99	8.606%	$181.3612	$181.36	$181.35	$181.40
7 purchase totals =	$957.40		$1,054.3227	$1,054.33	$1,054.35	$1,054.30