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	$179.80	3.388%	$185.8916	$185.89	$185.90	$185.90
Purchase #2	$59.79	10.508%	$66.0727	$66.07	$66.05	$66.10
Purchase #3	$185.54	5.308%	$195.3885	$195.39	$195.40	$195.40
Purchase #4	$155.93	5.440%	$164.4126	$164.41	$164.40	$164.40
Purchase #5	$98.96	5.128%	$104.0347	$104.03	$104.05	$104.00
Purchase #6	$124.75	7.549%	$134.1674	$134.17	$134.15	$134.20
Purchase #7	$74.39	10.417%	$82.1392	$82.14	$82.15	$82.10
7 purchase totals =	$879.16		$932.1067	$932.10	$932.10	$932.10