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	$141.96	7.589%	$152.7333	$152.73	$152.75	$152.70
Purchase #2	$52.52	12.544%	$59.1081	$59.11	$59.10	$59.10
Purchase #3	$39.75	9.450%	$43.5064	$43.51	$43.50	$43.50
Purchase #4	$72.82	7.330%	$78.1577	$78.16	$78.15	$78.20
Purchase #5	$137.64	3.345%	$142.2441	$142.24	$142.25	$142.20
Purchase #6	$158.54	8.411%	$171.8748	$171.87	$171.85	$171.90
Purchase #7	$200.25	9.647%	$219.5681	$219.57	$219.55	$219.60
7 purchase totals =	$803.48		$867.1925	$867.19	$867.15	$867.20