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	$58.44	7.661%	$62.9171	$62.92	$62.90	$62.90
Purchase #2	$41.88	4.142%	$43.6147	$43.61	$43.60	$43.60
Purchase #3	$75.83	8.441%	$82.2308	$82.23	$82.25	$82.20
Purchase #4	$88.45	13.399%	$100.3014	$100.30	$100.30	$100.30
Purchase #5	$244.73	10.374%	$270.1183	$270.12	$270.10	$270.10
Purchase #6	$230.51	9.550%	$252.5237	$252.52	$252.50	$252.50
Purchase #7	$104.28	4.864%	$109.3522	$109.35	$109.35	$109.40
7 purchase totals =	$844.12		$921.0582	$921.05	$921.00	$921.00