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	$176.77	4.178%	$184.1555	$184.16	$184.15	$184.20
Purchase #2	$76.92	6.760%	$82.1198	$82.12	$82.10	$82.10
Purchase #3	$199.43	10.573%	$220.5157	$220.52	$220.50	$220.50
Purchase #4	$137.33	9.791%	$150.776	$150.78	$150.80	$150.80
Purchase #5	$181.91	3.661%	$188.5697	$188.57	$188.55	$188.60
Purchase #6	$19.41	12.631%	$21.8617	$21.86	$21.85	$21.90
Purchase #7	$16.81	9.830%	$18.4624	$18.46	$18.45	$18.50
7 purchase totals =	$808.58		$866.4608	$866.47	$866.40	$866.60