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	$171.76	8.490%	$186.3424	$186.34	$186.35	$186.30
Purchase #2	$17.44	7.695%	$18.782	$18.78	$18.80	$18.80
Purchase #3	$136.43	3.703%	$141.482	$141.48	$141.50	$141.50
Purchase #4	$246.83	9.124%	$269.3508	$269.35	$269.35	$269.40
Purchase #5	$186.40	4.722%	$195.2018	$195.20	$195.20	$195.20
Purchase #6	$104.28	7.270%	$111.8612	$111.86	$111.85	$111.90
Purchase #7	$63.80	11.702%	$71.2659	$71.27	$71.25	$71.30
7 purchase totals =	$926.94		$994.2861	$994.28	$994.30	$994.40