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	$21.66	7.202%	$23.22	$23.22	$23.20	$23.20
Purchase #2	$38.25	13.424%	$43.3847	$43.38	$43.40	$43.40
Purchase #3	$170.41	6.364%	$181.2549	$181.25	$181.25	$181.30
Purchase #4	$151.47	3.512%	$156.7896	$156.79	$156.80	$156.80
Purchase #5	$203.44	9.727%	$223.2286	$223.23	$223.25	$223.20
Purchase #6	$59.30	13.749%	$67.4532	$67.45	$67.45	$67.50
Purchase #7	$57.77	6.337%	$61.4309	$61.43	$61.45	$61.40
7 purchase totals =	$702.30		$756.7619	$756.75	$756.80	$756.80