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	$194.82	8.763%	$211.8921	$211.89	$211.90	$211.90
Purchase #2	$228.67	9.681%	$250.8075	$250.81	$250.80	$250.80
Purchase #3	$208.29	6.696%	$222.2371	$222.24	$222.25	$222.20
Purchase #4	$103.34	7.489%	$111.0791	$111.08	$111.10	$111.10
Purchase #5	$246.27	9.833%	$270.4857	$270.49	$270.50	$270.50
Purchase #6	$173.57	8.486%	$188.2992	$188.30	$188.30	$188.30
Purchase #7	$120.52	5.576%	$127.2402	$127.24	$127.25	$127.20
7 purchase totals =	$1,275.48		$1,382.0409	$1,382.05	$1,382.10	$1,382.00