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	$86.82	6.260%	$92.2549	$92.25	$92.25	$92.30
Purchase #2	$118.59	10.492%	$131.0325	$131.03	$131.05	$131.00
Purchase #3	$242.67	11.855%	$271.4385	$271.44	$271.45	$271.40
Purchase #4	$203.35	6.303%	$216.1672	$216.17	$216.15	$216.20
Purchase #5	$219.63	5.784%	$232.3334	$232.33	$232.35	$232.30
Purchase #6	$128.90	10.812%	$142.8367	$142.84	$142.85	$142.80
Purchase #7	$54.82	11.651%	$61.2071	$61.21	$61.20	$61.20
7 purchase totals =	$1,054.78		$1,147.2703	$1,147.27	$1,147.30	$1,147.20