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	$175.30	8.463%	$190.1356	$190.14	$190.15	$190.10
Purchase #2	$173.88	6.481%	$185.1492	$185.15	$185.15	$185.10
Purchase #3	$222.51	4.874%	$233.3551	$233.36	$233.35	$233.40
Purchase #4	$40.83	3.627%	$42.3109	$42.31	$42.30	$42.30
Purchase #5	$170.57	5.312%	$179.6307	$179.63	$179.65	$179.60
Purchase #6	$19.62	10.317%	$21.6442	$21.64	$21.65	$21.60
Purchase #7	$219.31	3.339%	$226.6328	$226.63	$226.65	$226.60
7 purchase totals =	$1,022.02		$1,078.8585	$1,078.86	$1,078.90	$1,078.70